SEC Info  
    Home      Search      My Interests      Help      Sign In      Please Sign In

Qualys, Inc. – ‘10-K’ for 12/31/23 – ‘EX-101.DEF’

On:  Thursday, 2/22/24, at 5:07pm ET   ·   For:  12/31/23   ·   Accession #:  1107843-24-8   ·   File #:  1-35662

Previous ‘10-K’:  ‘10-K’ on 2/23/23 for 12/31/22   ·   Latest ‘10-K’:  This Filing   ·   11 References:   

Find Words in Filings emoji
 
  in    Show  and   Hints

  As Of               Filer                 Filing    For·On·As Docs:Size

 2/22/24  Qualys, Inc.                      10-K       12/31/23  103:11M

Annual Report   —   Form 10-K   —   SEA’34

Filing Table of Contents

Document/Exhibit                   Description                      Pages   Size 

 1: 10-K        Annual Report                                       HTML   1.94M 
 2: EX-10.10    Material Contract                                   HTML     36K 
 3: EX-21.1     Subsidiaries List                                   HTML     32K 
 4: EX-23.1     Consent of Expert or Counsel                        HTML     28K 
 9: EX-97.1     Clawback Policy re: Recovery of Erroneously         HTML     48K 
                Awarded Compensation                                             
 5: EX-31.1     Certification -- §302 - SOA'02                      HTML     33K 
 6: EX-31.2     Certification -- §302 - SOA'02                      HTML     33K 
 7: EX-32.1     Certification -- §906 - SOA'02                      HTML     30K 
 8: EX-32.2     Certification -- §906 - SOA'02                      HTML     30K 
15: R1          Cover                                               HTML     95K 
16: R2          Audit Information                                   HTML     34K 
17: R3          Consolidated Balance Sheets                         HTML    142K 
18: R4          Consolidated Balance Sheets (Parenthetical)         HTML     52K 
19: R5          Consolidated Statements of Operations               HTML    110K 
20: R6          Consolidated Statements of Comprehensive Income     HTML     55K 
21: R7          Consolidated Statements of Cash Flows               HTML    126K 
22: R8          Consolidated Statements of Stockholders' Equity     HTML     96K 
23: R9          The Company and Summary of Significant Accounting   HTML     79K 
                Policies                                                         
24: R10         Fair Value of Financial Instruments                 HTML    214K 
25: R11         Accumulated Other Comprehensive Income (Loss)       HTML     74K 
26: R12         Property and Equipment, Net                         HTML     44K 
27: R13         Revenue from Contracts With Customers               HTML     58K 
28: R14         Acquisitions                                        HTML     33K 
29: R15         Intangible Assets, Net                              HTML     66K 
30: R16         Leases                                              HTML     69K 
31: R17         Commitment and Contingencies                        HTML     39K 
32: R18         Stockholders' Equity and Stock-based Compensation   HTML    117K 
33: R19         Employee Benefit Plan                               HTML     33K 
34: R20         Income Taxes                                        HTML    118K 
35: R21         Segment and Geographic Area Information             HTML     50K 
36: R22         Net Income Per Share                                HTML     57K 
37: R23         Pay vs Performance Disclosure                       HTML     41K 
38: R24         Insider Trading Arrangements                        HTML     48K 
39: R25         The Company and Summary of Significant Accounting   HTML    133K 
                Policies (Policies)                                              
40: R26         Fair Value of Financial Instruments (Tables)        HTML    215K 
41: R27         Accumulated Other Comprehensive Income (Loss)       HTML     76K 
                (Tables)                                                         
42: R28         Property and Equipment, Net (Tables)                HTML     41K 
43: R29         Revenue from Contracts With Customers (Tables)      HTML     53K 
44: R30         Intangible Assets, Net (Tables)                     HTML    101K 
45: R31         Leases (Tables)                                     HTML     52K 
46: R32         Commitment and Contingencies (Tables)               HTML     34K 
47: R33         Stockholders' Equity and Stock-based Compensation   HTML    100K 
                (Tables)                                                         
48: R34         Income Taxes (Tables)                               HTML    117K 
49: R35         Segment and Geographic Area Information (Tables)    HTML     46K 
50: R36         Net Income Per Share (Tables)                       HTML     59K 
51: R37         The Company and Summary of Significant Accounting   HTML     72K 
                Policies - Narrative (Details)                                   
52: R38         Fair Value of Financial Instruments - Fair Value    HTML     65K 
                Hierarchy (Details)                                              
53: R39         Fair Value of Financial Instruments - Cash and      HTML     81K 
                Cash Equivalents (Details)                                       
54: R40         Fair Value of Financial Instruments - Summary of    HTML     71K 
                Securities in Unrealized Loss Positions (Details)                
55: R41         Fair Value of Financial Instruments - Summary of    HTML     57K 
                the Fair Value of Marketable Securities (Details)                
56: R42         Fair Value of Financial Instruments - Narrative     HTML     44K 
                (Details)                                                        
57: R43         Fair Value of Financial Instruments - Summary of    HTML     37K 
                Derivative Financial Instruments (Details)                       
58: R44         Fair Value of Financial Instruments - Amounts       HTML     37K 
                Recognized In Statement of Operations (Details)                  
59: R45         Accumulated Other Comprehensive Income (Loss) -     HTML     57K 
                Accumulated Other Comprehensive Income (Loss)                    
                (Details)                                                        
60: R46         Accumulated Other Comprehensive Income (Loss) -     HTML     71K 
                Amounts Reclassified from AOCI (Details)                         
61: R47         Property and Equipment, Net - Schedule of Property  HTML     48K 
                and Equipment, Net (Details)                                     
62: R48         Property and Equipment, Net - Narrative (Details)   HTML     39K 
63: R49         Revenue from Contracts With Customers - Narrative   HTML     37K 
                (Details)                                                        
64: R50         Revenue from Contracts with Customers - Expected    HTML     48K 
                Revenue from All Remaining Performance Obligations               
                (Details)                                                        
65: R51         Revenue from Contracts With Customers - Revenue by  HTML     39K 
                Sales Channel (Details)                                          
66: R52         Revenue from Contracts With Customers -             HTML     33K 
                Capitalized Cost to Obtain Contracts, Current and                
                Noncurrent (Details)                                             
67: R53         Acquisitions (Details)                              HTML     61K 
68: R54         Intangible Assets, Net - Carrying Value of          HTML     55K 
                Intangible Assets (Details)                                      
69: R55         Intangible Assets, Net (Details)                    HTML     31K 
70: R56         Intangible Assets, Net - Expected Amortization      HTML     40K 
                Expense in Future Periods (Details)                              
71: R57         Leases - Narrative (Details)                        HTML     30K 
72: R58         Leases - Supplemental Cash Flow Information         HTML     33K 
                (Details)                                                        
73: R59         Leases - Weighted Average Remaining Lease Term and  HTML     33K 
                Weighted Average Discount Rate (Details)                         
74: R60         Leases - Minimum Annual Lease Payments (Details)    HTML     49K 
75: R61         Commitment and Contingencies - Remaining Purchase   HTML     38K 
                Commitments (Details)                                            
76: R62         Stockholders' Equity and Stock-based Compensation   HTML     39K 
                - Preferred Stock (Details)                                      
77: R63         Stockholders' Equity and Stock-based Compensation   HTML     73K 
                - Equity Incentive Plan (Details)                                
78: R64         Stockholders' Equity and Stock-based Compensation   HTML     49K 
                - Summary of Stock-based Compensation Expense                    
                (Details)                                                        
79: R65         Stockholders' Equity and Stock-based Compensation   HTML     60K 
                - Stock-based Compensation (Details)                             
80: R66         Stockholders' Equity and Stock-based Compensation   HTML    137K 
                - Performance-Based Stock Options and Restricted                 
                Stock Units (Details)                                            
81: R67         Stockholders' Equity and Stock-based Compensation   HTML     54K 
                - Fair Value Assumptions, Stock Options (Details)                
82: R68         Stockholders' Equity and Stock-based Compensation   HTML     83K 
                - Share-based Compensation and Stock Options                     
                Activity (Details)                                               
83: R69         Stockholders' Equity and Stock-based Compensation   HTML     80K 
                - Summary of Restricted Stock Unit Activity                      
                (Details)                                                        
84: R70         Stockholders' Equity and Stock-based Compensation   HTML     45K 
                - Narrative (Details)                                            
85: R71         Stockholders' Equity and Stock-based Compensation   HTML     56K 
                - Employee Stock Purchase Plan, Valuation                        
                Assumptions (Details)                                            
86: R72         Stockholders' Equity and Stock-based Compensation   HTML     31K 
                - Schedule of Repurchase Agreements (Details)                    
87: R73         Stockholders' Equity and Stock-based Compensation   HTML     54K 
                - Share Repurchase Program (Details)                             
88: R74         Employee Benefit Plan (Details)                     HTML     32K 
89: R75         Income Taxes - Schedule of Income before Income     HTML     38K 
                Tax, Domestic and Foreign (Details)                              
90: R76         Income Taxes - Schedule of Components of Income     HTML     57K 
                Tax Expense (Benefit) (Details)                                  
91: R77         Income Taxes - Schedule of Effective Income Tax     HTML     54K 
                Rate Reconciliation (Details)                                    
92: R78         Income Taxes - Schedule of Deferred Tax Assets and  HTML     67K 
                Liabilities (Details)                                            
93: R79         Income Taxes - Narrative (Details)                  HTML     39K 
94: R80         Income Taxes - Schedule of Unrecognized Tax         HTML     41K 
                Benefits Roll Forward (Details)                                  
95: R81         Segment and Geographic Area Information -           HTML     33K 
                Narrative (Details)                                              
96: R82         Segment and Geographic Area Information - Revenue   HTML     45K 
                and Property and Equipment, Net by Geographic Area               
                (Details)                                                        
97: R83         Net Income Per Share - Basic and Diluted Net        HTML     72K 
                Income Per Share (Details)                                       
98: R84         Net Income Per Share - Anti-dilutive Net Income     HTML     39K 
                Per Share (Details)                                              
100: XML         IDEA XML File -- Filing Summary                      XML    186K  
103: XML         XBRL Instance -- qlys-20231231_htm                   XML   2.44M  
99: EXCEL       IDEA Workbook of Financial Report Info              XLSX    195K 
11: EX-101.CAL  XBRL Calculations -- qlys-20231231_cal               XML    281K 
12: EX-101.DEF  XBRL Definitions -- qlys-20231231_def                XML    589K 
13: EX-101.LAB  XBRL Labels -- qlys-20231231_lab                     XML   2.13M 
14: EX-101.PRE  XBRL Presentations -- qlys-20231231_pre              XML   1.25M 
10: EX-101.SCH  XBRL Schema -- qlys-20231231                         XSD    174K 
101: JSON        XBRL Instance as JSON Data -- MetaLinks              590±   905K  
102: ZIP         XBRL Zipped Folder -- 0001107843-24-000008-xbrl      Zip    891K  


‘EX-101.DEF’   —   XBRL Definitions — qlys-20231231_def


This Exhibit is an XBRL File.


                                                                                                                                                                                
<?xml version="1.0" encoding="windows-1252"?>
<!-- XBRL Document Created with the Workiva Platform -->
<!-- Copyright 2024 Workiva -->
<!-- r:f4ea1f53-8015-46e0-94c5-3054ac171407,g:ad08069b-edd9-4caa-93e6-69d8513fda7d -->
<link:linkbase xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
<link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all"/>
<link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension"/>
<link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default"/>
<link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain"/>
<link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member"/>
<link:roleRef roleURI="http://www.qualys.com/role/ConsolidatedStatementsofStockholdersEquity" xlink:type="simple" xlink:href="qlys-20231231.xsd#ConsolidatedStatementsofStockholdersEquity"/>
<link:definitionLink xlink:role="http://www.qualys.com/role/ConsolidatedStatementsofStockholdersEquity" xlink:type="extended">
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_ebe5e4d7-a349-48f2-b38b-d40b6cd55ac8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementLineItems"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_c90c6ef2-e194-466e-ae30-905d9cb2d423" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_ebe5e4d7-a349-48f2-b38b-d40b6cd55ac8" xlink:to="loc_us-gaap_StatementTable_c90c6ef2-e194-466e-ae30-905d9cb2d423" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_ed461016-cef5-4443-8b1e-748a0b528ed2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementEquityComponentsAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_c90c6ef2-e194-466e-ae30-905d9cb2d423" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_ed461016-cef5-4443-8b1e-748a0b528ed2" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_ed461016-cef5-4443-8b1e-748a0b528ed2_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquityComponentDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_ed461016-cef5-4443-8b1e-748a0b528ed2" xlink:to="loc_us-gaap_EquityComponentDomain_ed461016-cef5-4443-8b1e-748a0b528ed2_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_32ad43b1-4c0a-4bf8-a7aa-4a9783bc510a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquityComponentDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_ed461016-cef5-4443-8b1e-748a0b528ed2" xlink:to="loc_us-gaap_EquityComponentDomain_32ad43b1-4c0a-4bf8-a7aa-4a9783bc510a" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_6f62ac97-3eb6-46b8-b160-af76b98c95d5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_32ad43b1-4c0a-4bf8-a7aa-4a9783bc510a" xlink:to="loc_us-gaap_CommonStockMember_6f62ac97-3eb6-46b8-b160-af76b98c95d5" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_2261c709-954c-42e8-8339-1e0dcd287cf8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AdditionalPaidInCapitalMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_32ad43b1-4c0a-4bf8-a7aa-4a9783bc510a" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_2261c709-954c-42e8-8339-1e0dcd287cf8" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_b2a6334f-fdf5-4851-bc5b-95829e82f441" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_32ad43b1-4c0a-4bf8-a7aa-4a9783bc510a" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_b2a6334f-fdf5-4851-bc5b-95829e82f441" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_5153253e-c9fd-495e-bb67-c86085d34887" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RetainedEarningsMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_32ad43b1-4c0a-4bf8-a7aa-4a9783bc510a" xlink:to="loc_us-gaap_RetainedEarningsMember_5153253e-c9fd-495e-bb67-c86085d34887" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_fd9c1dd9-3500-4955-b106-6e83bd15caae" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_ebe5e4d7-a349-48f2-b38b-d40b6cd55ac8" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_fd9c1dd9-3500-4955-b106-6e83bd15caae" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharesOutstanding_be251cbe-46f6-4d26-83dc-9e0116d421c8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SharesOutstanding"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_fd9c1dd9-3500-4955-b106-6e83bd15caae" xlink:to="loc_us-gaap_SharesOutstanding_be251cbe-46f6-4d26-83dc-9e0116d421c8" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_7d1f1d6b-a79f-4731-8df9-c7ee883ed7d5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockholdersEquity"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_fd9c1dd9-3500-4955-b106-6e83bd15caae" xlink:to="loc_us-gaap_StockholdersEquity_7d1f1d6b-a79f-4731-8df9-c7ee883ed7d5" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_699de1cc-6a13-43a7-b239-f5fff9d2c80d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetIncomeLoss"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_fd9c1dd9-3500-4955-b106-6e83bd15caae" xlink:to="loc_us-gaap_NetIncomeLoss_699de1cc-6a13-43a7-b239-f5fff9d2c80d" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_6d7f7829-42cf-4f28-84c9-11cb694e5a56" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_fd9c1dd9-3500-4955-b106-6e83bd15caae" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_6d7f7829-42cf-4f28-84c9-11cb694e5a56" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_21b5c68f-d08f-4511-9e72-b14a524e5a91" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_fd9c1dd9-3500-4955-b106-6e83bd15caae" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_21b5c68f-d08f-4511-9e72-b14a524e5a91" xlink:type="arc" order="5"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised_13757b21-df24-42d8-bc8c-e9908959f8ee" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_fd9c1dd9-3500-4955-b106-6e83bd15caae" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised_13757b21-df24-42d8-bc8c-e9908959f8ee" xlink:type="arc" order="6"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchasedDuringPeriodShares_9a7dd28c-ec0c-4e16-9992-65be198c193a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockRepurchasedDuringPeriodShares"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_fd9c1dd9-3500-4955-b106-6e83bd15caae" xlink:to="loc_us-gaap_StockRepurchasedDuringPeriodShares_9a7dd28c-ec0c-4e16-9992-65be198c193a" xlink:type="arc" order="7"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchasedDuringPeriodValue_bb166b45-468a-4e95-8fc9-c010fe15abff" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockRepurchasedDuringPeriodValue"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_fd9c1dd9-3500-4955-b106-6e83bd15caae" xlink:to="loc_us-gaap_StockRepurchasedDuringPeriodValue_bb166b45-468a-4e95-8fc9-c010fe15abff" xlink:type="arc" order="8"/>
<link:loc xlink:type="locator" xlink:label="loc_qlys_StockIssuedDuringPeriodSharesRestrictedStockAwardVested_0fd16c3e-2860-40f9-b3e3-ac39f25b34af" xlink:href="qlys-20231231.xsd#qlys_StockIssuedDuringPeriodSharesRestrictedStockAwardVested"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_fd9c1dd9-3500-4955-b106-6e83bd15caae" xlink:to="loc_qlys_StockIssuedDuringPeriodSharesRestrictedStockAwardVested_0fd16c3e-2860-40f9-b3e3-ac39f25b34af" xlink:type="arc" order="9"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharesPaidForTaxWithholdingForShareBasedCompensation_dab199f3-e7da-4f3a-b848-7029d31ee435" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SharesPaidForTaxWithholdingForShareBasedCompensation"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_fd9c1dd9-3500-4955-b106-6e83bd15caae" xlink:to="loc_us-gaap_SharesPaidForTaxWithholdingForShareBasedCompensation_dab199f3-e7da-4f3a-b848-7029d31ee435" xlink:type="arc" order="10"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation_eae337f4-7d70-4edd-818f-f3e6d449cef3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_fd9c1dd9-3500-4955-b106-6e83bd15caae" xlink:to="loc_us-gaap_AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation_eae337f4-7d70-4edd-818f-f3e6d449cef3" xlink:type="arc" order="11"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans_38f2d018-180e-4b1b-b4d3-96517a1940da" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_fd9c1dd9-3500-4955-b106-6e83bd15caae" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans_38f2d018-180e-4b1b-b4d3-96517a1940da" xlink:type="arc" order="12"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueEmployeeStockPurchasePlan_f4efd4bd-905d-4bc8-9f51-8116d0e8bdba" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodValueEmployeeStockPurchasePlan"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_fd9c1dd9-3500-4955-b106-6e83bd15caae" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueEmployeeStockPurchasePlan_f4efd4bd-905d-4bc8-9f51-8116d0e8bdba" xlink:type="arc" order="13"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_cbfa7100-d4ff-4126-8308-432d38482b3d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_fd9c1dd9-3500-4955-b106-6e83bd15caae" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_cbfa7100-d4ff-4126-8308-432d38482b3d" xlink:type="arc" order="14"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharesOutstanding_63460251-dcba-411e-ae95-fad012fb1727" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SharesOutstanding"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_4dc033c5-6c97-47d8-8c5d-cfca56f2df81" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockholdersEquity"/>
</link:definitionLink>
<link:roleRef roleURI="http://www.qualys.com/role/TheCompanyandSummaryofSignificantAccountingPoliciesNarrativeDetails" xlink:type="simple" xlink:href="qlys-20231231.xsd#TheCompanyandSummaryofSignificantAccountingPoliciesNarrativeDetails"/>
<link:definitionLink xlink:role="http://www.qualys.com/role/TheCompanyandSummaryofSignificantAccountingPoliciesNarrativeDetails" xlink:type="extended">
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashAndCashEquivalentsItemsLineItems_9d38ae4b-f41d-4bd9-96ca-767e96dcdbb3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestrictedCashAndCashEquivalentsItemsLineItems"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRestrictedCashAndCashEquivalentsTable_b2f34747-f3ed-47d6-b938-cdcbd8f9b0a9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfRestrictedCashAndCashEquivalentsTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RestrictedCashAndCashEquivalentsItemsLineItems_9d38ae4b-f41d-4bd9-96ca-767e96dcdbb3" xlink:to="loc_us-gaap_ScheduleOfRestrictedCashAndCashEquivalentsTable_b2f34747-f3ed-47d6-b938-cdcbd8f9b0a9" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsAxis_42e2cfc9-9a21-4869-99c8-71c89f85f950" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRestrictedCashAndCashEquivalentsTable_b2f34747-f3ed-47d6-b938-cdcbd8f9b0a9" xlink:to="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsAxis_42e2cfc9-9a21-4869-99c8-71c89f85f950" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_42e2cfc9-9a21-4869-99c8-71c89f85f950_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsAxis_42e2cfc9-9a21-4869-99c8-71c89f85f950" xlink:to="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_42e2cfc9-9a21-4869-99c8-71c89f85f950_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_e890b0f2-610a-465e-8996-6a0ec9b053ab" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsAxis_42e2cfc9-9a21-4869-99c8-71c89f85f950" xlink:to="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_e890b0f2-610a-465e-8996-6a0ec9b053ab" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_qlys_CashHeldInEscrowWithBlueHexagonAcquisitionMember_d81e63c1-1933-440b-870c-4e80ba22ee31" xlink:href="qlys-20231231.xsd#qlys_CashHeldInEscrowWithBlueHexagonAcquisitionMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_e890b0f2-610a-465e-8996-6a0ec9b053ab" xlink:to="loc_qlys_CashHeldInEscrowWithBlueHexagonAcquisitionMember_d81e63c1-1933-440b-870c-4e80ba22ee31" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_qlys_SecurityDepositsMember_adeaff66-b2d3-48cb-a547-e45c5aca67d4" xlink:href="qlys-20231231.xsd#qlys_SecurityDepositsMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_e890b0f2-610a-465e-8996-6a0ec9b053ab" xlink:to="loc_qlys_SecurityDepositsMember_adeaff66-b2d3-48cb-a547-e45c5aca67d4" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_PledgingPurposeAxis_24ac6396-d4af-4a8d-b200-be96fab98d6a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PledgingPurposeAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRestrictedCashAndCashEquivalentsTable_b2f34747-f3ed-47d6-b938-cdcbd8f9b0a9" xlink:to="loc_us-gaap_PledgingPurposeAxis_24ac6396-d4af-4a8d-b200-be96fab98d6a" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_PledgingPurposeDomain_24ac6396-d4af-4a8d-b200-be96fab98d6a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PledgingPurposeDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PledgingPurposeAxis_24ac6396-d4af-4a8d-b200-be96fab98d6a" xlink:to="loc_us-gaap_PledgingPurposeDomain_24ac6396-d4af-4a8d-b200-be96fab98d6a_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_PledgingPurposeDomain_90f7ed27-2b07-44c0-a7f0-252e791b6baf" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PledgingPurposeDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PledgingPurposeAxis_24ac6396-d4af-4a8d-b200-be96fab98d6a" xlink:to="loc_us-gaap_PledgingPurposeDomain_90f7ed27-2b07-44c0-a7f0-252e791b6baf" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_LetterOfCreditMember_2e770a04-9e1b-4525-a41b-df146781ab3e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LetterOfCreditMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PledgingPurposeDomain_90f7ed27-2b07-44c0-a7f0-252e791b6baf" xlink:to="loc_us-gaap_LetterOfCreditMember_2e770a04-9e1b-4525-a41b-df146781ab3e" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_6c15e41b-e729-4897-ae3b-06dd3e8e451c" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRestrictedCashAndCashEquivalentsTable_b2f34747-f3ed-47d6-b938-cdcbd8f9b0a9" xlink:to="loc_srt_RangeAxis_6c15e41b-e729-4897-ae3b-06dd3e8e451c" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_6c15e41b-e729-4897-ae3b-06dd3e8e451c_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_6c15e41b-e729-4897-ae3b-06dd3e8e451c" xlink:to="loc_srt_RangeMember_6c15e41b-e729-4897-ae3b-06dd3e8e451c_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_9753fe65-da42-4d9b-9d1e-42127eb45f97" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_6c15e41b-e729-4897-ae3b-06dd3e8e451c" xlink:to="loc_srt_RangeMember_9753fe65-da42-4d9b-9d1e-42127eb45f97" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_15a65821-352b-4e26-9fb3-a8adbfa688cf" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MinimumMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_9753fe65-da42-4d9b-9d1e-42127eb45f97" xlink:to="loc_srt_MinimumMember_15a65821-352b-4e26-9fb3-a8adbfa688cf" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_29091bc5-647e-440b-8908-36fe84655b2d" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MaximumMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_9753fe65-da42-4d9b-9d1e-42127eb45f97" xlink:to="loc_srt_MaximumMember_29091bc5-647e-440b-8908-36fe84655b2d" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_c03538e7-baa3-4c84-a316-82c7eff629f5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRestrictedCashAndCashEquivalentsTable_b2f34747-f3ed-47d6-b938-cdcbd8f9b0a9" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_c03538e7-baa3-4c84-a316-82c7eff629f5" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_c03538e7-baa3-4c84-a316-82c7eff629f5_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_c03538e7-baa3-4c84-a316-82c7eff629f5" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_c03538e7-baa3-4c84-a316-82c7eff629f5_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_d7160d56-409f-4d49-8900-8e3712af4dd8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_c03538e7-baa3-4c84-a316-82c7eff629f5" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_d7160d56-409f-4d49-8900-8e3712af4dd8" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_qlys_ScannerAppliancesMember_b123cd44-8a94-4237-864b-4efb92e56d31" xlink:href="qlys-20231231.xsd#qlys_ScannerAppliancesMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_d7160d56-409f-4d49-8900-8e3712af4dd8" xlink:to="loc_qlys_ScannerAppliancesMember_b123cd44-8a94-4237-864b-4efb92e56d31" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_4eafe5d7-08c9-43ae-a439-bbbbb702f692" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRestrictedCashAndCashEquivalentsTable_b2f34747-f3ed-47d6-b938-cdcbd8f9b0a9" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_4eafe5d7-08c9-43ae-a439-bbbbb702f692" xlink:type="arc" order="5"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_4eafe5d7-08c9-43ae-a439-bbbbb702f692_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_4eafe5d7-08c9-43ae-a439-bbbbb702f692" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_4eafe5d7-08c9-43ae-a439-bbbbb702f692_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_20b8a288-d94f-4a30-b7bd-15e27dcc493c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_4eafe5d7-08c9-43ae-a439-bbbbb702f692" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_20b8a288-d94f-4a30-b7bd-15e27dcc493c" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_SoftwareAndSoftwareDevelopmentCostsMember_312790a8-c6f8-4b69-b02b-72d3ca7650f9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SoftwareAndSoftwareDevelopmentCostsMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_20b8a288-d94f-4a30-b7bd-15e27dcc493c" xlink:to="loc_us-gaap_SoftwareAndSoftwareDevelopmentCostsMember_312790a8-c6f8-4b69-b02b-72d3ca7650f9" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCash_d844a525-5fd7-489a-97c4-b990575014be" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestrictedCash"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestrictedCashAndCashEquivalentsItemsLineItems_9d38ae4b-f41d-4bd9-96ca-767e96dcdbb3" xlink:to="loc_us-gaap_RestrictedCash_d844a525-5fd7-489a-97c4-b990575014be" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsReceivableNet_4ddb9148-beaa-4af8-ad7d-a802399b56f7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccountsReceivableNet"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestrictedCashAndCashEquivalentsItemsLineItems_9d38ae4b-f41d-4bd9-96ca-767e96dcdbb3" xlink:to="loc_us-gaap_AccountsReceivableNet_4ddb9148-beaa-4af8-ad7d-a802399b56f7" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_Investments_db4ddfc4-5b9b-4409-95fd-e1bee07edca4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_Investments"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestrictedCashAndCashEquivalentsItemsLineItems_9d38ae4b-f41d-4bd9-96ca-767e96dcdbb3" xlink:to="loc_us-gaap_Investments_db4ddfc4-5b9b-4409-95fd-e1bee07edca4" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromDividendsReceived_8e759bb3-d039-42eb-87c3-224c87310a45" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProceedsFromDividendsReceived"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestrictedCashAndCashEquivalentsItemsLineItems_9d38ae4b-f41d-4bd9-96ca-767e96dcdbb3" xlink:to="loc_us-gaap_ProceedsFromDividendsReceived_8e759bb3-d039-42eb-87c3-224c87310a45" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsForAdvanceToAffiliate_8e4a0175-c985-429f-b4ac-5bb7873bb899" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PaymentsForAdvanceToAffiliate"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestrictedCashAndCashEquivalentsItemsLineItems_9d38ae4b-f41d-4bd9-96ca-767e96dcdbb3" xlink:to="loc_us-gaap_PaymentsForAdvanceToAffiliate_8e4a0175-c985-429f-b4ac-5bb7873bb899" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentUsefulLife_96d1092c-76aa-4bae-9e96-499cb3f282e1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentUsefulLife"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestrictedCashAndCashEquivalentsItemsLineItems_9d38ae4b-f41d-4bd9-96ca-767e96dcdbb3" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentUsefulLife_96d1092c-76aa-4bae-9e96-499cb3f282e1" xlink:type="arc" order="5"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ImpairmentOfLongLivedAssetsHeldForUse_368941d7-65cf-4f65-b97e-e017bc441112" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ImpairmentOfLongLivedAssetsHeldForUse"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestrictedCashAndCashEquivalentsItemsLineItems_9d38ae4b-f41d-4bd9-96ca-767e96dcdbb3" xlink:to="loc_us-gaap_ImpairmentOfLongLivedAssetsHeldForUse_368941d7-65cf-4f65-b97e-e017bc441112" xlink:type="arc" order="6"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_NumberOfReportingUnits_0b72c74e-229c-4ada-ad63-af52072188cc" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NumberOfReportingUnits"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestrictedCashAndCashEquivalentsItemsLineItems_9d38ae4b-f41d-4bd9-96ca-767e96dcdbb3" xlink:to="loc_us-gaap_NumberOfReportingUnits_0b72c74e-229c-4ada-ad63-af52072188cc" xlink:type="arc" order="7"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetUsefulLife_09e40804-9189-477f-8d5a-f0eda1f52d72" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetUsefulLife"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestrictedCashAndCashEquivalentsItemsLineItems_9d38ae4b-f41d-4bd9-96ca-767e96dcdbb3" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetUsefulLife_09e40804-9189-477f-8d5a-f0eda1f52d72" xlink:type="arc" order="8"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeTermOfContract_5f48f30c-0fa7-41e4-a345-25a4affc39b0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeTermOfContract"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestrictedCashAndCashEquivalentsItemsLineItems_9d38ae4b-f41d-4bd9-96ca-767e96dcdbb3" xlink:to="loc_us-gaap_DerivativeTermOfContract_5f48f30c-0fa7-41e4-a345-25a4affc39b0" xlink:type="arc" order="9"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_CapitalizedContractCostAmortizationPeriod_e6d1a485-6249-41b7-800b-cecf904dc2c6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CapitalizedContractCostAmortizationPeriod"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestrictedCashAndCashEquivalentsItemsLineItems_9d38ae4b-f41d-4bd9-96ca-767e96dcdbb3" xlink:to="loc_us-gaap_CapitalizedContractCostAmortizationPeriod_e6d1a485-6249-41b7-800b-cecf904dc2c6" xlink:type="arc" order="10"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdvertisingExpense_0a704ab7-5811-4796-bdea-4e0aad9ca8f6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AdvertisingExpense"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestrictedCashAndCashEquivalentsItemsLineItems_9d38ae4b-f41d-4bd9-96ca-767e96dcdbb3" xlink:to="loc_us-gaap_AdvertisingExpense_0a704ab7-5811-4796-bdea-4e0aad9ca8f6" xlink:type="arc" order="11"/>
</link:definitionLink>
<link:roleRef roleURI="http://www.qualys.com/role/FairValueofFinancialInstrumentsFairValueHierarchyDetails" xlink:type="simple" xlink:href="qlys-20231231.xsd#FairValueofFinancialInstrumentsFairValueHierarchyDetails"/>
<link:definitionLink xlink:role="http://www.qualys.com/role/FairValueofFinancialInstrumentsFairValueHierarchyDetails" xlink:type="extended">
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueOptionQuantitativeDisclosuresLineItems_dcabb05b-5ef1-41a5-bff1-3e746d5935af" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueOptionQuantitativeDisclosuresLineItems"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueOptionQuantitativeDisclosuresTable_db0f4c1d-a3c8-45c6-8d3a-713b4a4ef121" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueOptionQuantitativeDisclosuresTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueOptionQuantitativeDisclosuresLineItems_dcabb05b-5ef1-41a5-bff1-3e746d5935af" xlink:to="loc_us-gaap_FairValueOptionQuantitativeDisclosuresTable_db0f4c1d-a3c8-45c6-8d3a-713b4a4ef121" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_5037fe67-55b1-4111-b221-62f96454475d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueOptionQuantitativeDisclosuresTable_db0f4c1d-a3c8-45c6-8d3a-713b4a4ef121" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_5037fe67-55b1-4111-b221-62f96454475d" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_5037fe67-55b1-4111-b221-62f96454475d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_5037fe67-55b1-4111-b221-62f96454475d" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_5037fe67-55b1-4111-b221-62f96454475d_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_9d278bc8-2e1d-4a84-8cb8-7dab8e3131d0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_5037fe67-55b1-4111-b221-62f96454475d" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_9d278bc8-2e1d-4a84-8cb8-7dab8e3131d0" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_2808171f-f38f-4d66-b245-b83fb5c73ec9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueInputsLevel1Member"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_9d278bc8-2e1d-4a84-8cb8-7dab8e3131d0" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_2808171f-f38f-4d66-b245-b83fb5c73ec9" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_fbb75b89-0b28-477d-a0b6-778a5a7caa8d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueInputsLevel2Member"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_9d278bc8-2e1d-4a84-8cb8-7dab8e3131d0" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_fbb75b89-0b28-477d-a0b6-778a5a7caa8d" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByMeasurementFrequencyAxis_6fd6ed1f-2f1f-4aa9-8225-1079bd7281d6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueByMeasurementFrequencyAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueOptionQuantitativeDisclosuresTable_db0f4c1d-a3c8-45c6-8d3a-713b4a4ef121" xlink:to="loc_us-gaap_FairValueByMeasurementFrequencyAxis_6fd6ed1f-2f1f-4aa9-8225-1079bd7281d6" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_6fd6ed1f-2f1f-4aa9-8225-1079bd7281d6_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_6fd6ed1f-2f1f-4aa9-8225-1079bd7281d6" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_6fd6ed1f-2f1f-4aa9-8225-1079bd7281d6_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_f8d3dff7-41b0-443e-8976-a8f4b37660c7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_6fd6ed1f-2f1f-4aa9-8225-1079bd7281d6" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_f8d3dff7-41b0-443e-8976-a8f4b37660c7" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsRecurringMember_7e17cfdc-aaaa-4e5f-b071-0a33a83b2a81" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementsRecurringMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementFrequencyDomain_f8d3dff7-41b0-443e-8976-a8f4b37660c7" xlink:to="loc_us-gaap_FairValueMeasurementsRecurringMember_7e17cfdc-aaaa-4e5f-b071-0a33a83b2a81" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_MoneyMarketFundsAtCarryingValue_c4c64d17-73aa-47fc-bd4b-1bd2fdf32611" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_MoneyMarketFundsAtCarryingValue"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueOptionQuantitativeDisclosuresLineItems_dcabb05b-5ef1-41a5-bff1-3e746d5935af" xlink:to="loc_us-gaap_MoneyMarketFundsAtCarryingValue_c4c64d17-73aa-47fc-bd4b-1bd2fdf32611" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialPaperAtCarryingValue_3d32bdd8-2906-434c-ae2c-ea1a5f4a2891" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommercialPaperAtCarryingValue"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueOptionQuantitativeDisclosuresLineItems_dcabb05b-5ef1-41a5-bff1-3e746d5935af" xlink:to="loc_us-gaap_CommercialPaperAtCarryingValue_3d32bdd8-2906-434c-ae2c-ea1a5f4a2891" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_USGovernmentAgenciesSecuritiesAtCarryingValue_6312c064-3c37-4fbe-92d9-4e6c889a61fa" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_USGovernmentAgenciesSecuritiesAtCarryingValue"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueOptionQuantitativeDisclosuresLineItems_dcabb05b-5ef1-41a5-bff1-3e746d5935af" xlink:to="loc_us-gaap_USGovernmentAgenciesSecuritiesAtCarryingValue_6312c064-3c37-4fbe-92d9-4e6c889a61fa" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentsOwnedOtherSovereignGovernmentObligationsAtFairValue_3d2d502c-ba8b-4518-ae04-c68e1b04c56f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FinancialInstrumentsOwnedOtherSovereignGovernmentObligationsAtFairValue"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueOptionQuantitativeDisclosuresLineItems_dcabb05b-5ef1-41a5-bff1-3e746d5935af" xlink:to="loc_us-gaap_FinancialInstrumentsOwnedOtherSovereignGovernmentObligationsAtFairValue_3d2d502c-ba8b-4518-ae04-c68e1b04c56f" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentsOwnedCorporateDebtAtFairValue_cecc6514-7644-43e2-bd31-d5c9c3557b7d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FinancialInstrumentsOwnedCorporateDebtAtFairValue"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueOptionQuantitativeDisclosuresLineItems_dcabb05b-5ef1-41a5-bff1-3e746d5935af" xlink:to="loc_us-gaap_FinancialInstrumentsOwnedCorporateDebtAtFairValue_cecc6514-7644-43e2-bd31-d5c9c3557b7d" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetBackedSecuritiesAtCarryingValue_e82719d0-4f2d-4e5c-9ae1-4f3e43835193" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AssetBackedSecuritiesAtCarryingValue"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueOptionQuantitativeDisclosuresLineItems_dcabb05b-5ef1-41a5-bff1-3e746d5935af" xlink:to="loc_us-gaap_AssetBackedSecuritiesAtCarryingValue_e82719d0-4f2d-4e5c-9ae1-4f3e43835193" xlink:type="arc" order="5"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentsOwnedDerivativesAndOtherContractualAgreementsAtFairValue_41740a92-eb8d-4a01-b9af-31a11d68b6cc" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FinancialInstrumentsOwnedDerivativesAndOtherContractualAgreementsAtFairValue"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueOptionQuantitativeDisclosuresLineItems_dcabb05b-5ef1-41a5-bff1-3e746d5935af" xlink:to="loc_us-gaap_FinancialInstrumentsOwnedDerivativesAndOtherContractualAgreementsAtFairValue_41740a92-eb8d-4a01-b9af-31a11d68b6cc" xlink:type="arc" order="6"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentsOwnedAtFairValue_03af5cce-c1bc-4323-9586-1a03e314eccb" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FinancialInstrumentsOwnedAtFairValue"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueOptionQuantitativeDisclosuresLineItems_dcabb05b-5ef1-41a5-bff1-3e746d5935af" xlink:to="loc_us-gaap_FinancialInstrumentsOwnedAtFairValue_03af5cce-c1bc-4323-9586-1a03e314eccb" xlink:type="arc" order="7"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignCurrencyContractsLiabilityFairValueDisclosure_fb6c915c-98a6-43eb-8394-2dc4bfbccefe" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ForeignCurrencyContractsLiabilityFairValueDisclosure"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueOptionQuantitativeDisclosuresLineItems_dcabb05b-5ef1-41a5-bff1-3e746d5935af" xlink:to="loc_us-gaap_ForeignCurrencyContractsLiabilityFairValueDisclosure_fb6c915c-98a6-43eb-8394-2dc4bfbccefe" xlink:type="arc" order="8"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialLiabilitiesFairValueDisclosure_99f256cc-f508-4a20-adcc-77ec551c5e1d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FinancialLiabilitiesFairValueDisclosure"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueOptionQuantitativeDisclosuresLineItems_dcabb05b-5ef1-41a5-bff1-3e746d5935af" xlink:to="loc_us-gaap_FinancialLiabilitiesFairValueDisclosure_99f256cc-f508-4a20-adcc-77ec551c5e1d" xlink:type="arc" order="9"/>
</link:definitionLink>
<link:roleRef roleURI="http://www.qualys.com/role/FairValueofFinancialInstrumentsCashandCashEquivalentsDetails" xlink:type="simple" xlink:href="qlys-20231231.xsd#FairValueofFinancialInstrumentsCashandCashEquivalentsDetails"/>
<link:definitionLink xlink:role="http://www.qualys.com/role/FairValueofFinancialInstrumentsCashandCashEquivalentsDetails" xlink:type="extended">
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativesFairValueLineItems_2a958861-37a3-40e8-ab98-18503cb8df18" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativesFairValueLineItems"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueOptionQuantitativeDisclosuresTable_ba94bb9d-fb94-4b68-9290-f78f7c377b8d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueOptionQuantitativeDisclosuresTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_2a958861-37a3-40e8-ab98-18503cb8df18" xlink:to="loc_us-gaap_FairValueOptionQuantitativeDisclosuresTable_ba94bb9d-fb94-4b68-9290-f78f7c377b8d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAxis_c094bb9f-89f5-4018-8b38-6885ec6bd315" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CashAndCashEquivalentsAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueOptionQuantitativeDisclosuresTable_ba94bb9d-fb94-4b68-9290-f78f7c377b8d" xlink:to="loc_us-gaap_CashAndCashEquivalentsAxis_c094bb9f-89f5-4018-8b38-6885ec6bd315" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_c094bb9f-89f5-4018-8b38-6885ec6bd315_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CashAndCashEquivalentsAxis_c094bb9f-89f5-4018-8b38-6885ec6bd315" xlink:to="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_c094bb9f-89f5-4018-8b38-6885ec6bd315_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_708d75f5-3243-40b0-a3bc-f50eca6a212c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CashAndCashEquivalentsAxis_c094bb9f-89f5-4018-8b38-6885ec6bd315" xlink:to="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_708d75f5-3243-40b0-a3bc-f50eca6a212c" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_MoneyMarketFundsMember_50cae922-befe-4d83-b119-70022e67d6a5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_MoneyMarketFundsMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_708d75f5-3243-40b0-a3bc-f50eca6a212c" xlink:to="loc_us-gaap_MoneyMarketFundsMember_50cae922-befe-4d83-b119-70022e67d6a5" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_USGovernmentCorporationsAndAgenciesSecuritiesMember_85fb775f-9d67-48b2-b053-feeddc3132b1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_USGovernmentCorporationsAndAgenciesSecuritiesMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_708d75f5-3243-40b0-a3bc-f50eca6a212c" xlink:to="loc_us-gaap_USGovernmentCorporationsAndAgenciesSecuritiesMember_85fb775f-9d67-48b2-b053-feeddc3132b1" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_da94b540-ae14-411f-9e8f-7ef745acd1bb" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FinancialInstrumentAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueOptionQuantitativeDisclosuresTable_ba94bb9d-fb94-4b68-9290-f78f7c377b8d" xlink:to="loc_us-gaap_FinancialInstrumentAxis_da94b540-ae14-411f-9e8f-7ef745acd1bb" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_da94b540-ae14-411f-9e8f-7ef745acd1bb_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_da94b540-ae14-411f-9e8f-7ef745acd1bb" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_da94b540-ae14-411f-9e8f-7ef745acd1bb_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_68de5ff3-1df6-4340-ad6c-60fd36b5d676" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_da94b540-ae14-411f-9e8f-7ef745acd1bb" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_68de5ff3-1df6-4340-ad6c-60fd36b5d676" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialPaperNotIncludedWithCashAndCashEquivalentsMember_2303d26a-70ba-486c-a43c-a9efbe2ac9dc" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommercialPaperNotIncludedWithCashAndCashEquivalentsMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_68de5ff3-1df6-4340-ad6c-60fd36b5d676" xlink:to="loc_us-gaap_CommercialPaperNotIncludedWithCashAndCashEquivalentsMember_2303d26a-70ba-486c-a43c-a9efbe2ac9dc" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateDebtSecuritiesMember_71f92ca3-18fb-4cfe-a602-7e345aeb5b93" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CorporateDebtSecuritiesMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_68de5ff3-1df6-4340-ad6c-60fd36b5d676" xlink:to="loc_us-gaap_CorporateDebtSecuritiesMember_71f92ca3-18fb-4cfe-a602-7e345aeb5b93" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetBackedSecuritiesMember_ae915ded-e275-4c3b-89ec-92df06bf5b93" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AssetBackedSecuritiesMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_68de5ff3-1df6-4340-ad6c-60fd36b5d676" xlink:to="loc_us-gaap_AssetBackedSecuritiesMember_ae915ded-e275-4c3b-89ec-92df06bf5b93" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_USGovernmentAgenciesDebtSecuritiesMember_3777b7e4-e71d-485b-b21c-605637cc748f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_USGovernmentAgenciesDebtSecuritiesMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_68de5ff3-1df6-4340-ad6c-60fd36b5d676" xlink:to="loc_us-gaap_USGovernmentAgenciesDebtSecuritiesMember_3777b7e4-e71d-485b-b21c-605637cc748f" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_qlys_ForeignGovernmentAgenciesMember_e8c10d7a-0265-42d8-8315-07663292fe70" xlink:href="qlys-20231231.xsd#qlys_ForeignGovernmentAgenciesMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_68de5ff3-1df6-4340-ad6c-60fd36b5d676" xlink:to="loc_qlys_ForeignGovernmentAgenciesMember_e8c10d7a-0265-42d8-8315-07663292fe70" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByAssetClassAxis_ee1c884f-480f-4398-a2a9-22f92666e150" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueByAssetClassAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueOptionQuantitativeDisclosuresTable_ba94bb9d-fb94-4b68-9290-f78f7c377b8d" xlink:to="loc_us-gaap_FairValueByAssetClassAxis_ee1c884f-480f-4398-a2a9-22f92666e150" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_ee1c884f-480f-4398-a2a9-22f92666e150_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByAssetClassAxis_ee1c884f-480f-4398-a2a9-22f92666e150" xlink:to="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_ee1c884f-480f-4398-a2a9-22f92666e150_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_5880f940-1d8c-409e-b6c9-ea465a422cc1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByAssetClassAxis_ee1c884f-480f-4398-a2a9-22f92666e150" xlink:to="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_5880f940-1d8c-409e-b6c9-ea465a422cc1" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashEquivalentsMember_adff6eef-31f1-45b3-9f79-1f12b0bfc084" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CashEquivalentsMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_5880f940-1d8c-409e-b6c9-ea465a422cc1" xlink:to="loc_us-gaap_CashEquivalentsMember_adff6eef-31f1-45b3-9f79-1f12b0bfc084" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermInvestmentsMember_88510161-64fe-46d6-b425-19781aa09be0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShortTermInvestmentsMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_5880f940-1d8c-409e-b6c9-ea465a422cc1" xlink:to="loc_us-gaap_ShortTermInvestmentsMember_88510161-64fe-46d6-b425-19781aa09be0" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLongTermInvestmentsMember_68393ec6-44b3-4a6b-8470-613c7bf3d437" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherLongTermInvestmentsMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_5880f940-1d8c-409e-b6c9-ea465a422cc1" xlink:to="loc_us-gaap_OtherLongTermInvestmentsMember_68393ec6-44b3-4a6b-8470-613c7bf3d437" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_3f0b9f16-2a12-428f-96e4-1bb008ea7cc0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_2a958861-37a3-40e8-ab98-18503cb8df18" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_3f0b9f16-2a12-428f-96e4-1bb008ea7cc0" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_6f0b4804-8877-4030-a012-e66663b24cfb" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_2a958861-37a3-40e8-ab98-18503cb8df18" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_6f0b4804-8877-4030-a012-e66663b24cfb" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_8ec4c1e2-a6a3-4fa4-96c2-e8cd41eb27a4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_2a958861-37a3-40e8-ab98-18503cb8df18" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_8ec4c1e2-a6a3-4fa4-96c2-e8cd41eb27a4" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_81add350-5a93-4c06-bba6-b344d03c9ca1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecurities"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_2a958861-37a3-40e8-ab98-18503cb8df18" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_81add350-5a93-4c06-bba6-b344d03c9ca1" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_Cash_146e15f9-0735-42a0-b17e-431008b94931" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_Cash"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_2a958861-37a3-40e8-ab98-18503cb8df18" xlink:to="loc_us-gaap_Cash_146e15f9-0735-42a0-b17e-431008b94931" xlink:type="arc" order="4"/>
</link:definitionLink>
<link:roleRef roleURI="http://www.qualys.com/role/FairValueofFinancialInstrumentsSummaryofSecuritiesinUnrealizedLossPositionsDetails" xlink:type="simple" xlink:href="qlys-20231231.xsd#FairValueofFinancialInstrumentsSummaryofSecuritiesinUnrealizedLossPositionsDetails"/>
<link:definitionLink xlink:role="http://www.qualys.com/role/FairValueofFinancialInstrumentsSummaryofSecuritiesinUnrealizedLossPositionsDetails" xlink:type="extended">
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueDisclosureAssetAndLiabilityNotMeasuredAtFairValueLineItems_472329a7-e798-4ac2-af17-3fe00d5ff9d3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueDisclosureAssetAndLiabilityNotMeasuredAtFairValueLineItems"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueDisclosureOfAssetAndLiabilityNotMeasuredAtFairValueTable_b11bf892-d1fa-4ad9-b0cb-160b3a20998c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueDisclosureOfAssetAndLiabilityNotMeasuredAtFairValueTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueDisclosureAssetAndLiabilityNotMeasuredAtFairValueLineItems_472329a7-e798-4ac2-af17-3fe00d5ff9d3" xlink:to="loc_us-gaap_FairValueDisclosureOfAssetAndLiabilityNotMeasuredAtFairValueTable_b11bf892-d1fa-4ad9-b0cb-160b3a20998c" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_ee7cd8b2-e1c8-4cae-856b-3c0ab59fca2e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FinancialInstrumentAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueDisclosureOfAssetAndLiabilityNotMeasuredAtFairValueTable_b11bf892-d1fa-4ad9-b0cb-160b3a20998c" xlink:to="loc_us-gaap_FinancialInstrumentAxis_ee7cd8b2-e1c8-4cae-856b-3c0ab59fca2e" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_ee7cd8b2-e1c8-4cae-856b-3c0ab59fca2e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_ee7cd8b2-e1c8-4cae-856b-3c0ab59fca2e" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_ee7cd8b2-e1c8-4cae-856b-3c0ab59fca2e_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_b9a49c51-ffd1-4bb8-bbb9-a035b55079c2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_ee7cd8b2-e1c8-4cae-856b-3c0ab59fca2e" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_b9a49c51-ffd1-4bb8-bbb9-a035b55079c2" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialPaperNotIncludedWithCashAndCashEquivalentsMember_383560a8-9bb6-4b25-9cfc-a67afecf11ae" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommercialPaperNotIncludedWithCashAndCashEquivalentsMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_b9a49c51-ffd1-4bb8-bbb9-a035b55079c2" xlink:to="loc_us-gaap_CommercialPaperNotIncludedWithCashAndCashEquivalentsMember_383560a8-9bb6-4b25-9cfc-a67afecf11ae" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_qlys_ForeignGovernmentAgenciesMember_fb8b390a-aa97-4d7f-8a14-88640b3ee35a" xlink:href="qlys-20231231.xsd#qlys_ForeignGovernmentAgenciesMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_b9a49c51-ffd1-4bb8-bbb9-a035b55079c2" xlink:to="loc_qlys_ForeignGovernmentAgenciesMember_fb8b390a-aa97-4d7f-8a14-88640b3ee35a" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetBackedSecuritiesMember_6f845d8b-5cd6-407e-b6e1-4bb62c629a96" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AssetBackedSecuritiesMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_b9a49c51-ffd1-4bb8-bbb9-a035b55079c2" xlink:to="loc_us-gaap_AssetBackedSecuritiesMember_6f845d8b-5cd6-407e-b6e1-4bb62c629a96" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateDebtSecuritiesMember_830c3ef4-13f9-4064-ae4d-5b1f24b974c2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CorporateDebtSecuritiesMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_b9a49c51-ffd1-4bb8-bbb9-a035b55079c2" xlink:to="loc_us-gaap_CorporateDebtSecuritiesMember_830c3ef4-13f9-4064-ae4d-5b1f24b974c2" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_USGovernmentAgenciesDebtSecuritiesMember_73b34a20-2fa3-4f6f-9ccd-c003dfa91f0a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_USGovernmentAgenciesDebtSecuritiesMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_b9a49c51-ffd1-4bb8-bbb9-a035b55079c2" xlink:to="loc_us-gaap_USGovernmentAgenciesDebtSecuritiesMember_73b34a20-2fa3-4f6f-9ccd-c003dfa91f0a" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesCurrentAbstract_5512143c-6624-4fdf-827e-1c2b27fa0b82" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtSecuritiesCurrentAbstract"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueDisclosureAssetAndLiabilityNotMeasuredAtFairValueLineItems_472329a7-e798-4ac2-af17-3fe00d5ff9d3" xlink:to="loc_us-gaap_DebtSecuritiesCurrentAbstract_5512143c-6624-4fdf-827e-1c2b27fa0b82" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months_deb38f31-949a-455a-9d5d-9c09b03ec0b4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtSecuritiesCurrentAbstract_5512143c-6624-4fdf-827e-1c2b27fa0b82" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months_deb38f31-949a-455a-9d5d-9c09b03ec0b4" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss_e5258b29-1f51-45f0-bdd5-4f0dd1588c80" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtSecuritiesCurrentAbstract_5512143c-6624-4fdf-827e-1c2b27fa0b82" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss_e5258b29-1f51-45f0-bdd5-4f0dd1588c80" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesNoncurrentAbstract_572a502d-2584-47bd-9350-1166afee2187" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtSecuritiesNoncurrentAbstract"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueDisclosureAssetAndLiabilityNotMeasuredAtFairValueLineItems_472329a7-e798-4ac2-af17-3fe00d5ff9d3" xlink:to="loc_us-gaap_DebtSecuritiesNoncurrentAbstract_572a502d-2584-47bd-9350-1166afee2187" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger_323b0cd7-f154-478d-be52-a316a4777e70" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtSecuritiesNoncurrentAbstract_572a502d-2584-47bd-9350-1166afee2187" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger_323b0cd7-f154-478d-be52-a316a4777e70" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss_8e7ecfe9-13ad-4a4d-a287-d1f6c890ca48" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtSecuritiesNoncurrentAbstract_572a502d-2584-47bd-9350-1166afee2187" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss_8e7ecfe9-13ad-4a4d-a287-d1f6c890ca48" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAbstract_686798c4-ba4a-4888-9af1-ab963ac745bb" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtSecuritiesAbstract"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueDisclosureAssetAndLiabilityNotMeasuredAtFairValueLineItems_472329a7-e798-4ac2-af17-3fe00d5ff9d3" xlink:to="loc_us-gaap_DebtSecuritiesAbstract_686798c4-ba4a-4888-9af1-ab963ac745bb" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPosition_2e0c47d2-3791-47fb-87ca-729e4958af3b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPosition"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtSecuritiesAbstract_686798c4-ba4a-4888-9af1-ab963ac745bb" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPosition_2e0c47d2-3791-47fb-87ca-729e4958af3b" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPositionAccumulatedLoss_e7506d02-4ca4-4f55-9c78-849a9d37dd58" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPositionAccumulatedLoss"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtSecuritiesAbstract_686798c4-ba4a-4888-9af1-ab963ac745bb" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPositionAccumulatedLoss_e7506d02-4ca4-4f55-9c78-849a9d37dd58" xlink:type="arc" order="2"/>
</link:definitionLink>
<link:roleRef roleURI="http://www.qualys.com/role/FairValueofFinancialInstrumentsNarrativeDetails" xlink:type="simple" xlink:href="qlys-20231231.xsd#FairValueofFinancialInstrumentsNarrativeDetails"/>
<link:definitionLink xlink:role="http://www.qualys.com/role/FairValueofFinancialInstrumentsNarrativeDetails" xlink:type="extended">
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativesFairValueLineItems_4a442896-cf86-4fa3-8349-4334ce78b07d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativesFairValueLineItems"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_OffsettingAssetsTable_c0676053-47e6-4a47-8295-01f65ba4d344" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OffsettingAssetsTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_4a442896-cf86-4fa3-8349-4334ce78b07d" xlink:to="loc_us-gaap_OffsettingAssetsTable_c0676053-47e6-4a47-8295-01f65ba4d344" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_2e500c11-1a86-443d-835c-4b9213d7ff65" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_OffsettingAssetsTable_c0676053-47e6-4a47-8295-01f65ba4d344" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_2e500c11-1a86-443d-835c-4b9213d7ff65" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_2e500c11-1a86-443d-835c-4b9213d7ff65_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeContractTypeDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_2e500c11-1a86-443d-835c-4b9213d7ff65" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_2e500c11-1a86-443d-835c-4b9213d7ff65_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_850648a9-90f7-4b55-83df-1427fa667383" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeContractTypeDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_2e500c11-1a86-443d-835c-4b9213d7ff65" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_850648a9-90f7-4b55-83df-1427fa667383" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignExchangeContractMember_e63ac97d-de65-4782-8e1a-dc0f2209b81f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ForeignExchangeContractMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_850648a9-90f7-4b55-83df-1427fa667383" xlink:to="loc_us-gaap_ForeignExchangeContractMember_e63ac97d-de65-4782-8e1a-dc0f2209b81f" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_qlys_ForeignExchangeContractsForGBPAndEuroMember_b03123af-7bcb-4bc9-a358-605576e340c4" xlink:href="qlys-20231231.xsd#qlys_ForeignExchangeContractsForGBPAndEuroMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_850648a9-90f7-4b55-83df-1427fa667383" xlink:to="loc_qlys_ForeignExchangeContractsForGBPAndEuroMember_b03123af-7bcb-4bc9-a358-605576e340c4" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationAxis_8512fa18-28fe-4359-9032-cacd623a2ea7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_HedgingDesignationAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_OffsettingAssetsTable_c0676053-47e6-4a47-8295-01f65ba4d344" xlink:to="loc_us-gaap_HedgingDesignationAxis_8512fa18-28fe-4359-9032-cacd623a2ea7" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_8512fa18-28fe-4359-9032-cacd623a2ea7_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_HedgingDesignationDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_HedgingDesignationAxis_8512fa18-28fe-4359-9032-cacd623a2ea7" xlink:to="loc_us-gaap_HedgingDesignationDomain_8512fa18-28fe-4359-9032-cacd623a2ea7_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_efd9cc12-c5f3-44c3-9ed5-d238937613d7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_HedgingDesignationDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_HedgingDesignationAxis_8512fa18-28fe-4359-9032-cacd623a2ea7" xlink:to="loc_us-gaap_HedgingDesignationDomain_efd9cc12-c5f3-44c3-9ed5-d238937613d7" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DesignatedAsHedgingInstrumentMember_1010cfd3-2808-48c2-bb1c-f168604ad957" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DesignatedAsHedgingInstrumentMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingDesignationDomain_efd9cc12-c5f3-44c3-9ed5-d238937613d7" xlink:to="loc_us-gaap_DesignatedAsHedgingInstrumentMember_1010cfd3-2808-48c2-bb1c-f168604ad957" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_NondesignatedMember_2e42b54c-e93d-4f22-87fd-3a5fa0431e00" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NondesignatedMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingDesignationDomain_efd9cc12-c5f3-44c3-9ed5-d238937613d7" xlink:to="loc_us-gaap_NondesignatedMember_2e42b54c-e93d-4f22-87fd-3a5fa0431e00" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_d78d01d4-e6ec-4776-a6fe-2a74b9ca50f0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_OffsettingAssetsTable_c0676053-47e6-4a47-8295-01f65ba4d344" xlink:to="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_d78d01d4-e6ec-4776-a6fe-2a74b9ca50f0" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingRelationshipDomain_d78d01d4-e6ec-4776-a6fe-2a74b9ca50f0_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_HedgingRelationshipDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_d78d01d4-e6ec-4776-a6fe-2a74b9ca50f0" xlink:to="loc_us-gaap_HedgingRelationshipDomain_d78d01d4-e6ec-4776-a6fe-2a74b9ca50f0_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingRelationshipDomain_8e361749-cbd8-443b-b571-cda24cbbfb7c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_HedgingRelationshipDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_d78d01d4-e6ec-4776-a6fe-2a74b9ca50f0" xlink:to="loc_us-gaap_HedgingRelationshipDomain_8e361749-cbd8-443b-b571-cda24cbbfb7c" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashFlowHedgingMember_4f162548-9571-415a-bd36-5c09f5f592f5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CashFlowHedgingMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingRelationshipDomain_8e361749-cbd8-443b-b571-cda24cbbfb7c" xlink:to="loc_us-gaap_CashFlowHedgingMember_4f162548-9571-415a-bd36-5c09f5f592f5" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeNotionalAmount_b2e9b41e-6f66-4a55-b0a2-56e7c067ecaa" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeNotionalAmount"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_4a442896-cf86-4fa3-8349-4334ce78b07d" xlink:to="loc_us-gaap_DerivativeNotionalAmount_b2e9b41e-6f66-4a55-b0a2-56e7c067ecaa" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignCurrencyCashFlowHedgeGainLossToBeReclassifiedDuringNext12Months_02bd10a6-3aae-4b0f-a665-311ceb47008a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ForeignCurrencyCashFlowHedgeGainLossToBeReclassifiedDuringNext12Months"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_4a442896-cf86-4fa3-8349-4334ce78b07d" xlink:to="loc_us-gaap_ForeignCurrencyCashFlowHedgeGainLossToBeReclassifiedDuringNext12Months_02bd10a6-3aae-4b0f-a665-311ceb47008a" xlink:type="arc" order="1"/>
</link:definitionLink>
<link:roleRef roleURI="http://www.qualys.com/role/FairValueofFinancialInstrumentsSummaryofDerivativeFinancialInstrumentsDetails" xlink:type="simple" xlink:href="qlys-20231231.xsd#FairValueofFinancialInstrumentsSummaryofDerivativeFinancialInstrumentsDetails"/>
<link:definitionLink xlink:role="http://www.qualys.com/role/FairValueofFinancialInstrumentsSummaryofDerivativeFinancialInstrumentsDetails" xlink:type="extended">
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativesFairValueLineItems_6d251148-2c5d-4c87-b645-731c62ee4d63" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativesFairValueLineItems"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueOptionQuantitativeDisclosuresTable_6e7e3f05-992d-4626-8b2e-04ea02d60306" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueOptionQuantitativeDisclosuresTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_6d251148-2c5d-4c87-b645-731c62ee4d63" xlink:to="loc_us-gaap_FairValueOptionQuantitativeDisclosuresTable_6e7e3f05-992d-4626-8b2e-04ea02d60306" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationAxis_57adc63c-215b-406a-ab09-6898e3547214" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_HedgingDesignationAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueOptionQuantitativeDisclosuresTable_6e7e3f05-992d-4626-8b2e-04ea02d60306" xlink:to="loc_us-gaap_HedgingDesignationAxis_57adc63c-215b-406a-ab09-6898e3547214" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_57adc63c-215b-406a-ab09-6898e3547214_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_HedgingDesignationDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_HedgingDesignationAxis_57adc63c-215b-406a-ab09-6898e3547214" xlink:to="loc_us-gaap_HedgingDesignationDomain_57adc63c-215b-406a-ab09-6898e3547214_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_d19debfb-863b-4130-9f39-b67cd8a90586" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_HedgingDesignationDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_HedgingDesignationAxis_57adc63c-215b-406a-ab09-6898e3547214" xlink:to="loc_us-gaap_HedgingDesignationDomain_d19debfb-863b-4130-9f39-b67cd8a90586" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DesignatedAsHedgingInstrumentMember_a8f5040b-a251-4e39-b128-34d5df66c0de" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DesignatedAsHedgingInstrumentMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingDesignationDomain_d19debfb-863b-4130-9f39-b67cd8a90586" xlink:to="loc_us-gaap_DesignatedAsHedgingInstrumentMember_a8f5040b-a251-4e39-b128-34d5df66c0de" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_NondesignatedMember_d9991d18-428b-445e-81c5-d776263ec3cd" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NondesignatedMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingDesignationDomain_d19debfb-863b-4130-9f39-b67cd8a90586" xlink:to="loc_us-gaap_NondesignatedMember_d9991d18-428b-445e-81c5-d776263ec3cd" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignCurrencyContractAssetFairValueDisclosure_7a461527-c07f-40b9-ac94-a4c0e11c2659" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ForeignCurrencyContractAssetFairValueDisclosure"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_6d251148-2c5d-4c87-b645-731c62ee4d63" xlink:to="loc_us-gaap_ForeignCurrencyContractAssetFairValueDisclosure_7a461527-c07f-40b9-ac94-a4c0e11c2659" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignCurrencyContractsLiabilityFairValueDisclosure_3ba342f4-84fd-46e6-91f2-45a9aa832454" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ForeignCurrencyContractsLiabilityFairValueDisclosure"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_6d251148-2c5d-4c87-b645-731c62ee4d63" xlink:to="loc_us-gaap_ForeignCurrencyContractsLiabilityFairValueDisclosure_3ba342f4-84fd-46e6-91f2-45a9aa832454" xlink:type="arc" order="1"/>
</link:definitionLink>
<link:roleRef roleURI="http://www.qualys.com/role/AccumulatedOtherComprehensiveIncomeLossAccumulatedOtherComprehensiveIncomeLossDetails" xlink:type="simple" xlink:href="qlys-20231231.xsd#AccumulatedOtherComprehensiveIncomeLossAccumulatedOtherComprehensiveIncomeLossDetails"/>
<link:definitionLink xlink:role="http://www.qualys.com/role/AccumulatedOtherComprehensiveIncomeLossAccumulatedOtherComprehensiveIncomeLossDetails" xlink:type="extended">
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_7c6b3b3e-e03d-46bb-acac-f66bcc0057b6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_5f283f41-91c0-4744-9f12-99d272f6483e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_7c6b3b3e-e03d-46bb-acac-f66bcc0057b6" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_5f283f41-91c0-4744-9f12-99d272f6483e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_f8dd2d11-775f-45d8-a732-4e3ed8298942" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementEquityComponentsAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_5f283f41-91c0-4744-9f12-99d272f6483e" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_f8dd2d11-775f-45d8-a732-4e3ed8298942" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_f8dd2d11-775f-45d8-a732-4e3ed8298942_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquityComponentDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_f8dd2d11-775f-45d8-a732-4e3ed8298942" xlink:to="loc_us-gaap_EquityComponentDomain_f8dd2d11-775f-45d8-a732-4e3ed8298942_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_8db52e39-9e66-4bc1-bb75-01ed6bd2d7b8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquityComponentDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_f8dd2d11-775f-45d8-a732-4e3ed8298942" xlink:to="loc_us-gaap_EquityComponentDomain_8db52e39-9e66-4bc1-bb75-01ed6bd2d7b8" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_cf890a5f-487f-4cec-9ae1-7b35fab142e3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_8db52e39-9e66-4bc1-bb75-01ed6bd2d7b8" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_cf890a5f-487f-4cec-9ae1-7b35fab142e3" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember_92fae335-93d6-4e4a-a71f-7298b16cf028" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_cf890a5f-487f-4cec-9ae1-7b35fab142e3" xlink:to="loc_us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember_92fae335-93d6-4e4a-a71f-7298b16cf028" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedGainLossNetCashFlowHedgeParentMember_75e81228-f349-464c-8643-d53139c7638f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccumulatedGainLossNetCashFlowHedgeParentMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_cf890a5f-487f-4cec-9ae1-7b35fab142e3" xlink:to="loc_us-gaap_AccumulatedGainLossNetCashFlowHedgeParentMember_75e81228-f349-464c-8643-d53139c7638f" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_9a9adfff-8a0e-46e6-a2ad-a5e3f7863902" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AOCIAttributableToParentNetOfTaxRollForward"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_7c6b3b3e-e03d-46bb-acac-f66bcc0057b6" xlink:to="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_9a9adfff-8a0e-46e6-a2ad-a5e3f7863902" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_adbb807a-7b68-4d3d-86d2-5064a13610f7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockholdersEquity"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_9a9adfff-8a0e-46e6-a2ad-a5e3f7863902" xlink:to="loc_us-gaap_StockholdersEquity_adbb807a-7b68-4d3d-86d2-5064a13610f7" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_OciBeforeReclassificationsBeforeTaxAttributableToParent_ff28df7b-f4cb-4d58-ba75-9b55ca4d73e8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OciBeforeReclassificationsBeforeTaxAttributableToParent"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_9a9adfff-8a0e-46e6-a2ad-a5e3f7863902" xlink:to="loc_us-gaap_OciBeforeReclassificationsBeforeTaxAttributableToParent_ff28df7b-f4cb-4d58-ba75-9b55ca4d73e8" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationFromAociCurrentPeriodBeforeTaxAttributableToParent_8d131097-9f31-4870-9914-58208023f46d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ReclassificationFromAociCurrentPeriodBeforeTaxAttributableToParent"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_9a9adfff-8a0e-46e6-a2ad-a5e3f7863902" xlink:to="loc_us-gaap_ReclassificationFromAociCurrentPeriodBeforeTaxAttributableToParent_8d131097-9f31-4870-9914-58208023f46d" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossTaxPortionAttributableToParent1_19b882d6-a96f-493a-ad8d-64c457d7ff87" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherComprehensiveIncomeLossTaxPortionAttributableToParent1"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_9a9adfff-8a0e-46e6-a2ad-a5e3f7863902" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossTaxPortionAttributableToParent1_19b882d6-a96f-493a-ad8d-64c457d7ff87" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_3340fa5e-50c7-45af-8b02-3aec3c6fbe13" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_9a9adfff-8a0e-46e6-a2ad-a5e3f7863902" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_3340fa5e-50c7-45af-8b02-3aec3c6fbe13" xlink:type="arc" order="5"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_f0d4aa7b-2834-4089-a62c-3d769bf4c729" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockholdersEquity"/>
</link:definitionLink>
<link:roleRef roleURI="http://www.qualys.com/role/AccumulatedOtherComprehensiveIncomeLossAmountsReclassifiedfromAOCIDetails" xlink:type="simple" xlink:href="qlys-20231231.xsd#AccumulatedOtherComprehensiveIncomeLossAmountsReclassifiedfromAOCIDetails"/>
<link:definitionLink xlink:role="http://www.qualys.com/role/AccumulatedOtherComprehensiveIncomeLossAmountsReclassifiedfromAOCIDetails" xlink:type="extended">
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_1d11e02c-55ac-4758-a197-a82e82bfd583" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_8cd8e84f-88b6-4443-93c9-b46cff86b2ba" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_1d11e02c-55ac-4758-a197-a82e82bfd583" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_8cd8e84f-88b6-4443-93c9-b46cff86b2ba" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis_54dc66bf-ece0-4e08-818d-611a88776327" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_8cd8e84f-88b6-4443-93c9-b46cff86b2ba" xlink:to="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis_54dc66bf-ece0-4e08-818d-611a88776327" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeDomain_54dc66bf-ece0-4e08-818d-611a88776327_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis_54dc66bf-ece0-4e08-818d-611a88776327" xlink:to="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeDomain_54dc66bf-ece0-4e08-818d-611a88776327_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeDomain_ae10e627-9981-483f-9bef-83c61422c5c5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis_54dc66bf-ece0-4e08-818d-611a88776327" xlink:to="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeDomain_ae10e627-9981-483f-9bef-83c61422c5c5" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember_358c6efe-20bf-4f88-8a9f-12d08e319188" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeDomain_ae10e627-9981-483f-9bef-83c61422c5c5" xlink:to="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember_358c6efe-20bf-4f88-8a9f-12d08e319188" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_b94338ef-5e78-4635-ade1-c7884638351e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementEquityComponentsAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_8cd8e84f-88b6-4443-93c9-b46cff86b2ba" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_b94338ef-5e78-4635-ade1-c7884638351e" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_b94338ef-5e78-4635-ade1-c7884638351e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquityComponentDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_b94338ef-5e78-4635-ade1-c7884638351e" xlink:to="loc_us-gaap_EquityComponentDomain_b94338ef-5e78-4635-ade1-c7884638351e_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_dab74778-269f-4220-b58f-00b4e59e36a3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquityComponentDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_b94338ef-5e78-4635-ade1-c7884638351e" xlink:to="loc_us-gaap_EquityComponentDomain_dab74778-269f-4220-b58f-00b4e59e36a3" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember_0cad3af3-639c-4264-92a2-557bbe2a331f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_dab74778-269f-4220-b58f-00b4e59e36a3" xlink:to="loc_us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember_0cad3af3-639c-4264-92a2-557bbe2a331f" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedGainLossNetCashFlowHedgeParentMember_5bf79c33-ec42-4c88-a35d-da0a412dced7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccumulatedGainLossNetCashFlowHedgeParentMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_dab74778-269f-4220-b58f-00b4e59e36a3" xlink:to="loc_us-gaap_AccumulatedGainLossNetCashFlowHedgeParentMember_5bf79c33-ec42-4c88-a35d-da0a412dced7" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationFromAociCurrentPeriodTaxAbstract_976ec502-94c4-45c8-aaca-5309ff2b50ee" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ReclassificationFromAociCurrentPeriodTaxAbstract"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_1d11e02c-55ac-4758-a197-a82e82bfd583" xlink:to="loc_us-gaap_ReclassificationFromAociCurrentPeriodTaxAbstract_976ec502-94c4-45c8-aaca-5309ff2b50ee" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNonoperatingIncomeExpense_ff97ddde-6577-488c-ac4f-314896b9c513" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherNonoperatingIncomeExpense"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationFromAociCurrentPeriodTaxAbstract_976ec502-94c4-45c8-aaca-5309ff2b50ee" xlink:to="loc_us-gaap_OtherNonoperatingIncomeExpense_ff97ddde-6577-488c-ac4f-314896b9c513" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AOCIAttributableToParentAbstract_0e234316-e429-42ba-8de2-d833399d1b18" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AOCIAttributableToParentAbstract"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_1d11e02c-55ac-4758-a197-a82e82bfd583" xlink:to="loc_us-gaap_AOCIAttributableToParentAbstract_0e234316-e429-42ba-8de2-d833399d1b18" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_db4a7d01-f17c-409c-b8c9-f4bc739012fd" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentAbstract_0e234316-e429-42ba-8de2-d833399d1b18" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_db4a7d01-f17c-409c-b8c9-f4bc739012fd" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfRevenue_471c3736-baa9-4e25-bf9a-9abc407b3eba" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CostOfRevenue"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentAbstract_0e234316-e429-42ba-8de2-d833399d1b18" xlink:to="loc_us-gaap_CostOfRevenue_471c3736-baa9-4e25-bf9a-9abc407b3eba" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResearchAndDevelopmentExpense_fdcef6d4-7060-4d28-8d9f-2d3dbb9c6d3c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ResearchAndDevelopmentExpense"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentAbstract_0e234316-e429-42ba-8de2-d833399d1b18" xlink:to="loc_us-gaap_ResearchAndDevelopmentExpense_fdcef6d4-7060-4d28-8d9f-2d3dbb9c6d3c" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_SellingAndMarketingExpense_024d0fe4-0f5f-4c35-b95e-1cab775fd759" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SellingAndMarketingExpense"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentAbstract_0e234316-e429-42ba-8de2-d833399d1b18" xlink:to="loc_us-gaap_SellingAndMarketingExpense_024d0fe4-0f5f-4c35-b95e-1cab775fd759" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_GeneralAndAdministrativeExpense_08ccedda-c5cc-44bc-8cb2-cb1c4832236d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GeneralAndAdministrativeExpense"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentAbstract_0e234316-e429-42ba-8de2-d833399d1b18" xlink:to="loc_us-gaap_GeneralAndAdministrativeExpense_08ccedda-c5cc-44bc-8cb2-cb1c4832236d" xlink:type="arc" order="5"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_e427109d-2f14-4567-a969-43386ac81ee6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetIncomeLoss"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentAbstract_0e234316-e429-42ba-8de2-d833399d1b18" xlink:to="loc_us-gaap_NetIncomeLoss_e427109d-2f14-4567-a969-43386ac81ee6" xlink:type="arc" order="6"/>
</link:definitionLink>
<link:roleRef roleURI="http://www.qualys.com/role/PropertyandEquipmentNetScheduleofPropertyandEquipmentNetDetails" xlink:type="simple" xlink:href="qlys-20231231.xsd#PropertyandEquipmentNetScheduleofPropertyandEquipmentNetDetails"/>
<link:definitionLink xlink:role="http://www.qualys.com/role/PropertyandEquipmentNetScheduleofPropertyandEquipmentNetDetails" xlink:type="extended">
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentLineItems_11444224-55fc-4cfc-826c-c72e74f38454" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentLineItems"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_834ec886-183a-42b8-b8d9-5e3fa18e146d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfPropertyPlantAndEquipmentTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_11444224-55fc-4cfc-826c-c72e74f38454" xlink:to="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_834ec886-183a-42b8-b8d9-5e3fa18e146d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_efb27cff-23dc-48aa-9e69-36acb10fa154" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_834ec886-183a-42b8-b8d9-5e3fa18e146d" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_efb27cff-23dc-48aa-9e69-36acb10fa154" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_efb27cff-23dc-48aa-9e69-36acb10fa154_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_efb27cff-23dc-48aa-9e69-36acb10fa154" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_efb27cff-23dc-48aa-9e69-36acb10fa154_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_1aad3963-a05d-438d-994a-0457da09cf58" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_efb27cff-23dc-48aa-9e69-36acb10fa154" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_1aad3963-a05d-438d-994a-0457da09cf58" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ComputerEquipmentMember_447744c3-2fd4-4255-b501-d78ab68d1d81" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ComputerEquipmentMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_1aad3963-a05d-438d-994a-0457da09cf58" xlink:to="loc_us-gaap_ComputerEquipmentMember_447744c3-2fd4-4255-b501-d78ab68d1d81" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ComputerSoftwareIntangibleAssetMember_32a74b03-16be-439a-8755-f7453481ada6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ComputerSoftwareIntangibleAssetMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_1aad3963-a05d-438d-994a-0457da09cf58" xlink:to="loc_us-gaap_ComputerSoftwareIntangibleAssetMember_32a74b03-16be-439a-8755-f7453481ada6" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_LeaseholdImprovementsMember_5e96e5a8-2f5e-49de-a838-2d7078875cfc" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LeaseholdImprovementsMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_1aad3963-a05d-438d-994a-0457da09cf58" xlink:to="loc_us-gaap_LeaseholdImprovementsMember_5e96e5a8-2f5e-49de-a838-2d7078875cfc" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_qlys_ScannerAppliancesMember_5c97d9b2-35c3-4dd0-a861-34d8d5cad86e" xlink:href="qlys-20231231.xsd#qlys_ScannerAppliancesMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_1aad3963-a05d-438d-994a-0457da09cf58" xlink:to="loc_qlys_ScannerAppliancesMember_5c97d9b2-35c3-4dd0-a861-34d8d5cad86e" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FurnitureAndFixturesMember_583cca31-524b-4a0d-85ba-5c4c0823afc6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FurnitureAndFixturesMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_1aad3963-a05d-438d-994a-0457da09cf58" xlink:to="loc_us-gaap_FurnitureAndFixturesMember_583cca31-524b-4a0d-85ba-5c4c0823afc6" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetBeforeAccumulatedDepreciationAndAmortization_c497b572-e7c0-49c2-93f4-98605e1ad925" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetBeforeAccumulatedDepreciationAndAmortization"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_11444224-55fc-4cfc-826c-c72e74f38454" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetBeforeAccumulatedDepreciationAndAmortization_c497b572-e7c0-49c2-93f4-98605e1ad925" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_36a213e4-3fdf-4a2a-949e-b4eb195dde6c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_11444224-55fc-4cfc-826c-c72e74f38454" xlink:to="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_36a213e4-3fdf-4a2a-949e-b4eb195dde6c" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_b8ab5f60-f2d5-4761-8634-7b44af6e28fa" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentNet"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_11444224-55fc-4cfc-826c-c72e74f38454" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_b8ab5f60-f2d5-4761-8634-7b44af6e28fa" xlink:type="arc" order="2"/>
</link:definitionLink>
<link:roleRef roleURI="http://www.qualys.com/role/PropertyandEquipmentNetNarrativeDetails" xlink:type="simple" xlink:href="qlys-20231231.xsd#PropertyandEquipmentNetNarrativeDetails"/>
<link:definitionLink xlink:role="http://www.qualys.com/role/PropertyandEquipmentNetNarrativeDetails" xlink:type="extended">
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentLineItems_f65eb938-4438-4ffb-9839-b82d9ab62bd9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentLineItems"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_28228401-9f41-43ce-ae20-5ee3bbf6304f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfPropertyPlantAndEquipmentTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_f65eb938-4438-4ffb-9839-b82d9ab62bd9" xlink:to="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_28228401-9f41-43ce-ae20-5ee3bbf6304f" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_7c4e2d5a-1622-41ea-a231-c72339649f12" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_28228401-9f41-43ce-ae20-5ee3bbf6304f" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_7c4e2d5a-1622-41ea-a231-c72339649f12" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_7c4e2d5a-1622-41ea-a231-c72339649f12_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_7c4e2d5a-1622-41ea-a231-c72339649f12" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_7c4e2d5a-1622-41ea-a231-c72339649f12_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_693b25ba-006a-4547-b73c-b8da5d04385b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_7c4e2d5a-1622-41ea-a231-c72339649f12" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_693b25ba-006a-4547-b73c-b8da5d04385b" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_qlys_ScannerAppliancesAndOtherComputerEquipmentSubjectToSubscriptionMember_0905b681-0204-460c-ad05-f12435ab15f1" xlink:href="qlys-20231231.xsd#qlys_ScannerAppliancesAndOtherComputerEquipmentSubjectToSubscriptionMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_693b25ba-006a-4547-b73c-b8da5d04385b" xlink:to="loc_qlys_ScannerAppliancesAndOtherComputerEquipmentSubjectToSubscriptionMember_0905b681-0204-460c-ad05-f12435ab15f1" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_qlys_ScannerAppliancesAndOtherComputerEquipmentNotPlacedInServiceMember_ad85c147-193c-40e2-b3d2-ff90728f83ac" xlink:href="qlys-20231231.xsd#qlys_ScannerAppliancesAndOtherComputerEquipmentNotPlacedInServiceMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_693b25ba-006a-4547-b73c-b8da5d04385b" xlink:to="loc_qlys_ScannerAppliancesAndOtherComputerEquipmentNotPlacedInServiceMember_ad85c147-193c-40e2-b3d2-ff90728f83ac" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_496bfb6a-2aab-49f2-92ab-c9f57ef21f3c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentNet"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_f65eb938-4438-4ffb-9839-b82d9ab62bd9" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_496bfb6a-2aab-49f2-92ab-c9f57ef21f3c" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_qlys_DepreciationDepletionAndAmortizationExcludingIntangibleAssetAmortization_e8077eaf-e064-48b6-9fe3-bfacd0763bd6" xlink:href="qlys-20231231.xsd#qlys_DepreciationDepletionAndAmortizationExcludingIntangibleAssetAmortization"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_f65eb938-4438-4ffb-9839-b82d9ab62bd9" xlink:to="loc_qlys_DepreciationDepletionAndAmortizationExcludingIntangibleAssetAmortization_e8077eaf-e064-48b6-9fe3-bfacd0763bd6" xlink:type="arc" order="1"/>
</link:definitionLink>
<link:roleRef roleURI="http://www.qualys.com/role/RevenuefromContractswithCustomersExpectedRevenuefromAllRemainingPerformanceObligationsDetails" xlink:type="simple" xlink:href="qlys-20231231.xsd#RevenuefromContractswithCustomersExpectedRevenuefromAllRemainingPerformanceObligationsDetails"/>
<link:definitionLink xlink:role="http://www.qualys.com/role/RevenuefromContractswithCustomersExpectedRevenuefromAllRemainingPerformanceObligationsDetails" xlink:type="extended">
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_EntityWideInformationRevenueFromExternalCustomerLineItems_9fd53c7a-2706-4758-a9be-8670cc197539" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EntityWideInformationRevenueFromExternalCustomerLineItems"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable_7321869f-57cd-4d46-aafe-55f07bd0521d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_EntityWideInformationRevenueFromExternalCustomerLineItems_9fd53c7a-2706-4758-a9be-8670cc197539" xlink:to="loc_us-gaap_ScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable_7321869f-57cd-4d46-aafe-55f07bd0521d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis_f39a4c37-d52f-4b69-9133-269a11adef41" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable_7321869f-57cd-4d46-aafe-55f07bd0521d" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis_f39a4c37-d52f-4b69-9133-269a11adef41" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligation_815d729f-6f16-4cdd-83e6-a4f7b6d46f99" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevenueRemainingPerformanceObligation"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EntityWideInformationRevenueFromExternalCustomerLineItems_9fd53c7a-2706-4758-a9be-8670cc197539" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligation_815d729f-6f16-4cdd-83e6-a4f7b6d46f99" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_1b22e6af-9da8-4e0b-8a68-86f7c90ada74" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EntityWideInformationRevenueFromExternalCustomerLineItems_9fd53c7a-2706-4758-a9be-8670cc197539" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_1b22e6af-9da8-4e0b-8a68-86f7c90ada74" xlink:type="arc" order="1"/>
</link:definitionLink>
<link:roleRef roleURI="http://www.qualys.com/role/RevenuefromContractswithCustomersExpectedRevenuefromAllRemainingPerformanceObligationsDetails_1" xlink:type="simple" xlink:href="qlys-20231231.xsd#RevenuefromContractswithCustomersExpectedRevenuefromAllRemainingPerformanceObligationsDetails_1"/>
<link:definitionLink xlink:role="http://www.qualys.com/role/RevenuefromContractswithCustomersExpectedRevenuefromAllRemainingPerformanceObligationsDetails_1" xlink:type="extended">
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_EntityWideInformationRevenueFromExternalCustomerLineItems_9fd53c7a-2706-4758-a9be-8670cc197539" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EntityWideInformationRevenueFromExternalCustomerLineItems"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable_7321869f-57cd-4d46-aafe-55f07bd0521d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_EntityWideInformationRevenueFromExternalCustomerLineItems_9fd53c7a-2706-4758-a9be-8670cc197539" xlink:to="loc_us-gaap_ScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable_7321869f-57cd-4d46-aafe-55f07bd0521d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligation_815d729f-6f16-4cdd-83e6-a4f7b6d46f99" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevenueRemainingPerformanceObligation"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EntityWideInformationRevenueFromExternalCustomerLineItems_9fd53c7a-2706-4758-a9be-8670cc197539" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligation_815d729f-6f16-4cdd-83e6-a4f7b6d46f99" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_1b22e6af-9da8-4e0b-8a68-86f7c90ada74" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EntityWideInformationRevenueFromExternalCustomerLineItems_9fd53c7a-2706-4758-a9be-8670cc197539" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_1b22e6af-9da8-4e0b-8a68-86f7c90ada74" xlink:type="arc" order="1"/>
</link:definitionLink>
<link:roleRef roleURI="http://www.qualys.com/role/RevenuefromContractsWithCustomersRevenuebySalesChannelDetails" xlink:type="simple" xlink:href="qlys-20231231.xsd#RevenuefromContractsWithCustomersRevenuebySalesChannelDetails"/>
<link:definitionLink xlink:role="http://www.qualys.com/role/RevenuefromContractsWithCustomersRevenuebySalesChannelDetails" xlink:type="extended">
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_EntityWideInformationRevenueFromExternalCustomerLineItems_4bb821e6-834d-46f9-a2a9-915ccc6535c5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EntityWideInformationRevenueFromExternalCustomerLineItems"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable_cc5c8ef9-be93-4207-877f-e0bf80e9d927" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_EntityWideInformationRevenueFromExternalCustomerLineItems_4bb821e6-834d-46f9-a2a9-915ccc6535c5" xlink:to="loc_us-gaap_ScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable_cc5c8ef9-be93-4207-877f-e0bf80e9d927" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerSalesChannelAxis_43f6b74d-eceb-44f8-ba1b-72eb4eeacc2a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ContractWithCustomerSalesChannelAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable_cc5c8ef9-be93-4207-877f-e0bf80e9d927" xlink:to="loc_us-gaap_ContractWithCustomerSalesChannelAxis_43f6b74d-eceb-44f8-ba1b-72eb4eeacc2a" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerSalesChannelDomain_43f6b74d-eceb-44f8-ba1b-72eb4eeacc2a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ContractWithCustomerSalesChannelDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ContractWithCustomerSalesChannelAxis_43f6b74d-eceb-44f8-ba1b-72eb4eeacc2a" xlink:to="loc_us-gaap_ContractWithCustomerSalesChannelDomain_43f6b74d-eceb-44f8-ba1b-72eb4eeacc2a_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerSalesChannelDomain_eb3284a1-55a7-4b0d-a2ae-6e4de5637c4f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ContractWithCustomerSalesChannelDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ContractWithCustomerSalesChannelAxis_43f6b74d-eceb-44f8-ba1b-72eb4eeacc2a" xlink:to="loc_us-gaap_ContractWithCustomerSalesChannelDomain_eb3284a1-55a7-4b0d-a2ae-6e4de5637c4f" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_SalesChannelDirectlyToConsumerMember_5cdb3ca6-6d49-4ac6-9752-6fdd1867b77d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SalesChannelDirectlyToConsumerMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ContractWithCustomerSalesChannelDomain_eb3284a1-55a7-4b0d-a2ae-6e4de5637c4f" xlink:to="loc_us-gaap_SalesChannelDirectlyToConsumerMember_5cdb3ca6-6d49-4ac6-9752-6fdd1867b77d" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_SalesChannelThroughIntermediaryMember_951ecfc8-23c3-43a6-a037-aee081536caa" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SalesChannelThroughIntermediaryMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ContractWithCustomerSalesChannelDomain_eb3284a1-55a7-4b0d-a2ae-6e4de5637c4f" xlink:to="loc_us-gaap_SalesChannelThroughIntermediaryMember_951ecfc8-23c3-43a6-a037-aee081536caa" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_abdf90df-310f-40e2-8d96-5b5bbd32aba6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EntityWideInformationRevenueFromExternalCustomerLineItems_4bb821e6-834d-46f9-a2a9-915ccc6535c5" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_abdf90df-310f-40e2-8d96-5b5bbd32aba6" xlink:type="arc" order="0"/>
</link:definitionLink>
<link:roleRef roleURI="http://www.qualys.com/role/AcquisitionsDetails" xlink:type="simple" xlink:href="qlys-20231231.xsd#AcquisitionsDetails"/>
<link:definitionLink xlink:role="http://www.qualys.com/role/AcquisitionsDetails" xlink:type="extended">
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionLineItems_f572eba7-9222-439b-af53-1d811fdc8d3e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BusinessAcquisitionLineItems"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_a83b08e8-873b-4a24-b72e-f16966b985f5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_f572eba7-9222-439b-af53-1d811fdc8d3e" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_a83b08e8-873b-4a24-b72e-f16966b985f5" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetAcquisitionAxis_0c833149-1a8a-4ccf-bc1d-d3c47c4f6b83" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AssetAcquisitionAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_a83b08e8-873b-4a24-b72e-f16966b985f5" xlink:to="loc_us-gaap_AssetAcquisitionAxis_0c833149-1a8a-4ccf-bc1d-d3c47c4f6b83" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetAcquisitionDomain_0c833149-1a8a-4ccf-bc1d-d3c47c4f6b83_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AssetAcquisitionDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AssetAcquisitionAxis_0c833149-1a8a-4ccf-bc1d-d3c47c4f6b83" xlink:to="loc_us-gaap_AssetAcquisitionDomain_0c833149-1a8a-4ccf-bc1d-d3c47c4f6b83_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetAcquisitionDomain_e112f5a5-cc13-424a-8508-900c666451ac" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AssetAcquisitionDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AssetAcquisitionAxis_0c833149-1a8a-4ccf-bc1d-d3c47c4f6b83" xlink:to="loc_us-gaap_AssetAcquisitionDomain_e112f5a5-cc13-424a-8508-900c666451ac" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_qlys_BlueHexagonIncMember_bc877c82-c8bb-4147-a3dd-696e3374bb8e" xlink:href="qlys-20231231.xsd#qlys_BlueHexagonIncMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetAcquisitionDomain_e112f5a5-cc13-424a-8508-900c666451ac" xlink:to="loc_qlys_BlueHexagonIncMember_bc877c82-c8bb-4147-a3dd-696e3374bb8e" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_1dd0a664-f642-459f-8b25-118c28297413" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_a83b08e8-873b-4a24-b72e-f16966b985f5" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_1dd0a664-f642-459f-8b25-118c28297413" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_1dd0a664-f642-459f-8b25-118c28297413_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_1dd0a664-f642-459f-8b25-118c28297413" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_1dd0a664-f642-459f-8b25-118c28297413_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_446d8c7e-8f96-4265-95af-58618a351a98" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_1dd0a664-f642-459f-8b25-118c28297413" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_446d8c7e-8f96-4265-95af-58618a351a98" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DevelopedTechnologyRightsMember_da75c480-49dd-48bd-8c2b-e0ce99958c88" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DevelopedTechnologyRightsMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_446d8c7e-8f96-4265-95af-58618a351a98" xlink:to="loc_us-gaap_DevelopedTechnologyRightsMember_da75c480-49dd-48bd-8c2b-e0ce99958c88" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_qlys_AssembledWorkforceMember_ae29c995-8efd-4b83-9d44-68ca91f86c62" xlink:href="qlys-20231231.xsd#qlys_AssembledWorkforceMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_446d8c7e-8f96-4265-95af-58618a351a98" xlink:to="loc_qlys_AssembledWorkforceMember_ae29c995-8efd-4b83-9d44-68ca91f86c62" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetAcquisitionConsiderationTransferred_972912bd-b02d-4b75-b5e6-70e8b143a16b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AssetAcquisitionConsiderationTransferred"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_f572eba7-9222-439b-af53-1d811fdc8d3e" xlink:to="loc_us-gaap_AssetAcquisitionConsiderationTransferred_972912bd-b02d-4b75-b5e6-70e8b143a16b" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireProductiveAssets_fb52a274-cced-43c5-9b6c-3b804e902b38" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PaymentsToAcquireProductiveAssets"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_f572eba7-9222-439b-af53-1d811fdc8d3e" xlink:to="loc_us-gaap_PaymentsToAcquireProductiveAssets_fb52a274-cced-43c5-9b6c-3b804e902b38" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_qlys_AssetAcquisitionConsiderationTransferredPayable_d3d2ac09-b5b9-4ce6-bd55-dd8ecd8582ed" xlink:href="qlys-20231231.xsd#qlys_AssetAcquisitionConsiderationTransferredPayable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_f572eba7-9222-439b-af53-1d811fdc8d3e" xlink:to="loc_qlys_AssetAcquisitionConsiderationTransferredPayable_d3d2ac09-b5b9-4ce6-bd55-dd8ecd8582ed" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_qlys_AssetAcquisitionConsiderationPayableTerm_f43b3f6c-5cc1-4549-b2c5-71ed456bf251" xlink:href="qlys-20231231.xsd#qlys_AssetAcquisitionConsiderationPayableTerm"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_f572eba7-9222-439b-af53-1d811fdc8d3e" xlink:to="loc_qlys_AssetAcquisitionConsiderationPayableTerm_f43b3f6c-5cc1-4549-b2c5-71ed456bf251" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_qlys_AssetAcquisitionRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesDeferredRevenue_19b73cb0-c345-4923-ad74-7ea5a23b6949" xlink:href="qlys-20231231.xsd#qlys_AssetAcquisitionRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesDeferredRevenue"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_f572eba7-9222-439b-af53-1d811fdc8d3e" xlink:to="loc_qlys_AssetAcquisitionRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesDeferredRevenue_19b73cb0-c345-4923-ad74-7ea5a23b6949" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:label="loc_qlys_AssetAcquisitionAcquisitionRelatedCosts_420d36ed-4d76-4c4f-b2f0-707cf67672f0" xlink:href="qlys-20231231.xsd#qlys_AssetAcquisitionAcquisitionRelatedCosts"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_f572eba7-9222-439b-af53-1d811fdc8d3e" xlink:to="loc_qlys_AssetAcquisitionAcquisitionRelatedCosts_420d36ed-4d76-4c4f-b2f0-707cf67672f0" xlink:type="arc" order="5"/>
<link:loc xlink:type="locator" xlink:label="loc_qlys_AssetAcquisitionRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedFiniteLivedIntangibles_bd72bacf-ca3a-4ee8-a0a0-c744cdbbebdc" xlink:href="qlys-20231231.xsd#qlys_AssetAcquisitionRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedFiniteLivedIntangibles"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_f572eba7-9222-439b-af53-1d811fdc8d3e" xlink:to="loc_qlys_AssetAcquisitionRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedFiniteLivedIntangibles_bd72bacf-ca3a-4ee8-a0a0-c744cdbbebdc" xlink:type="arc" order="6"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetUsefulLife_255dcbef-7213-4df0-8a3e-854fb2b871a7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetUsefulLife"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_f572eba7-9222-439b-af53-1d811fdc8d3e" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetUsefulLife_255dcbef-7213-4df0-8a3e-854fb2b871a7" xlink:type="arc" order="7"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinitelivedIntangibleAssetsAcquired1_32a4c5d3-4f91-439e-aba6-b712bfaea627" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FinitelivedIntangibleAssetsAcquired1"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_f572eba7-9222-439b-af53-1d811fdc8d3e" xlink:to="loc_us-gaap_FinitelivedIntangibleAssetsAcquired1_32a4c5d3-4f91-439e-aba6-b712bfaea627" xlink:type="arc" order="8"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireIntangibleAssets_536ae646-ea7a-4820-bc69-c3c8146a096c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PaymentsToAcquireIntangibleAssets"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_f572eba7-9222-439b-af53-1d811fdc8d3e" xlink:to="loc_us-gaap_PaymentsToAcquireIntangibleAssets_536ae646-ea7a-4820-bc69-c3c8146a096c" xlink:type="arc" order="9"/>
</link:definitionLink>
<link:roleRef roleURI="http://www.qualys.com/role/IntangibleAssetsNetCarryingValueofIntangibleAssetsDetails" xlink:type="simple" xlink:href="qlys-20231231.xsd#IntangibleAssetsNetCarryingValueofIntangibleAssetsDetails"/>
<link:definitionLink xlink:role="http://www.qualys.com/role/IntangibleAssetsNetCarryingValueofIntangibleAssetsDetails" xlink:type="extended">
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_19d29e63-187a-431f-805f-0280fa91fa6d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetsLineItems"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_3cbf159a-db05-480b-8efe-028afe4d8133" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_19d29e63-187a-431f-805f-0280fa91fa6d" xlink:to="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_3cbf159a-db05-480b-8efe-028afe4d8133" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_532dd7a4-25eb-4026-af14-4b0cec5d7fd9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_3cbf159a-db05-480b-8efe-028afe4d8133" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_532dd7a4-25eb-4026-af14-4b0cec5d7fd9" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_532dd7a4-25eb-4026-af14-4b0cec5d7fd9_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_532dd7a4-25eb-4026-af14-4b0cec5d7fd9" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_532dd7a4-25eb-4026-af14-4b0cec5d7fd9_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_3f2631d5-0679-423a-a73f-147ffe709ba3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_532dd7a4-25eb-4026-af14-4b0cec5d7fd9" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_3f2631d5-0679-423a-a73f-147ffe709ba3" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DevelopedTechnologyRightsMember_b4df57fb-e998-4910-a678-ff096f53a3e0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DevelopedTechnologyRightsMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_3f2631d5-0679-423a-a73f-147ffe709ba3" xlink:to="loc_us-gaap_DevelopedTechnologyRightsMember_b4df57fb-e998-4910-a678-ff096f53a3e0" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_PatentsMember_6b5e0376-f371-4785-add3-e31f52adb3ac" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PatentsMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_3f2631d5-0679-423a-a73f-147ffe709ba3" xlink:to="loc_us-gaap_PatentsMember_6b5e0376-f371-4785-add3-e31f52adb3ac" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_qlys_AssembledWorkforceMember_88496552-0d9b-4748-9051-3c6ee59eab5f" xlink:href="qlys-20231231.xsd#qlys_AssembledWorkforceMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_3f2631d5-0679-423a-a73f-147ffe709ba3" xlink:to="loc_qlys_AssembledWorkforceMember_88496552-0d9b-4748-9051-3c6ee59eab5f" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetUsefulLife_d94ac02f-ff4b-42a9-bb4a-147ed514c891" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetUsefulLife"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_19d29e63-187a-431f-805f-0280fa91fa6d" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetUsefulLife_d94ac02f-ff4b-42a9-bb4a-147ed514c891" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsRemainingAmortizationPeriod1_e37b14bd-4ae4-42ca-b6ae-89057c090b9e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetsRemainingAmortizationPeriod1"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_19d29e63-187a-431f-805f-0280fa91fa6d" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsRemainingAmortizationPeriod1_e37b14bd-4ae4-42ca-b6ae-89057c090b9e" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsGross_7a814cb5-a7f9-4d64-b144-f465d552bbc5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetsGross"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_19d29e63-187a-431f-805f-0280fa91fa6d" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsGross_7a814cb5-a7f9-4d64-b144-f465d552bbc5" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_016c24e9-efb6-4748-a68f-9274d7475511" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_19d29e63-187a-431f-805f-0280fa91fa6d" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_016c24e9-efb6-4748-a68f-9274d7475511" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsNet_7c9827f7-b5f1-4955-b2c4-b1cdbd413b95" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetsNet"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_19d29e63-187a-431f-805f-0280fa91fa6d" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsNet_7c9827f7-b5f1-4955-b2c4-b1cdbd413b95" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill_0ae397c4-4f4d-4166-a339-aa405ba6d40a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_19d29e63-187a-431f-805f-0280fa91fa6d" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill_0ae397c4-4f4d-4166-a339-aa405ba6d40a" xlink:type="arc" order="5"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_b3b38bfd-c2df-4eb3-b819-99d1bad857cb" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IntangibleAssetsNetExcludingGoodwill"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_19d29e63-187a-431f-805f-0280fa91fa6d" xlink:to="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_b3b38bfd-c2df-4eb3-b819-99d1bad857cb" xlink:type="arc" order="6"/>
</link:definitionLink>
<link:roleRef roleURI="http://www.qualys.com/role/StockholdersEquityandStockbasedCompensationEquityIncentivePlanDetails" xlink:type="simple" xlink:href="qlys-20231231.xsd#StockholdersEquityandStockbasedCompensationEquityIncentivePlanDetails"/>
<link:definitionLink xlink:role="http://www.qualys.com/role/StockholdersEquityandStockbasedCompensationEquityIncentivePlanDetails" xlink:type="extended">
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_c8cfefef-4c5a-4cc2-aa6e-bd2e52f022d9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_d6533f8c-e0c1-499e-a943-47933cea5c85" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_c8cfefef-4c5a-4cc2-aa6e-bd2e52f022d9" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_d6533f8c-e0c1-499e-a943-47933cea5c85" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameAxis_e0b36a61-9096-4dac-ab37-fb0b55a53226" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PlanNameAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_d6533f8c-e0c1-499e-a943-47933cea5c85" xlink:to="loc_us-gaap_PlanNameAxis_e0b36a61-9096-4dac-ab37-fb0b55a53226" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_e0b36a61-9096-4dac-ab37-fb0b55a53226_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PlanNameDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PlanNameAxis_e0b36a61-9096-4dac-ab37-fb0b55a53226" xlink:to="loc_us-gaap_PlanNameDomain_e0b36a61-9096-4dac-ab37-fb0b55a53226_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_94acae0d-358d-4c9d-880b-16f6a9024957" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PlanNameDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PlanNameAxis_e0b36a61-9096-4dac-ab37-fb0b55a53226" xlink:to="loc_us-gaap_PlanNameDomain_94acae0d-358d-4c9d-880b-16f6a9024957" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_qlys_The2012EquityIncentivePlanMember_980e2510-8f3a-437a-9dcf-67099cd26382" xlink:href="qlys-20231231.xsd#qlys_The2012EquityIncentivePlanMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_94acae0d-358d-4c9d-880b-16f6a9024957" xlink:to="loc_qlys_The2012EquityIncentivePlanMember_980e2510-8f3a-437a-9dcf-67099cd26382" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_qlys_The2021EmployeeStockPurchasePlanMember_dad23d5d-b59c-49bb-9ddb-edb3d1ce0a3d" xlink:href="qlys-20231231.xsd#qlys_The2021EmployeeStockPurchasePlanMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_94acae0d-358d-4c9d-880b-16f6a9024957" xlink:to="loc_qlys_The2021EmployeeStockPurchasePlanMember_dad23d5d-b59c-49bb-9ddb-edb3d1ce0a3d" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_b9a01abb-ea49-414a-9026-bca3278cbf4b" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_d6533f8c-e0c1-499e-a943-47933cea5c85" xlink:to="loc_srt_RangeAxis_b9a01abb-ea49-414a-9026-bca3278cbf4b" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_b9a01abb-ea49-414a-9026-bca3278cbf4b_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_b9a01abb-ea49-414a-9026-bca3278cbf4b" xlink:to="loc_srt_RangeMember_b9a01abb-ea49-414a-9026-bca3278cbf4b_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_8653d206-cd64-4ffa-9b8e-1ac5c1e75958" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_b9a01abb-ea49-414a-9026-bca3278cbf4b" xlink:to="loc_srt_RangeMember_8653d206-cd64-4ffa-9b8e-1ac5c1e75958" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_081a3e13-b5bd-468d-8fce-72972ca5485b" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MinimumMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_8653d206-cd64-4ffa-9b8e-1ac5c1e75958" xlink:to="loc_srt_MinimumMember_081a3e13-b5bd-468d-8fce-72972ca5485b" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_b2eb08e2-b648-4485-90f4-ee3fd5b0c575" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MaximumMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_8653d206-cd64-4ffa-9b8e-1ac5c1e75958" xlink:to="loc_srt_MaximumMember_b2eb08e2-b648-4485-90f4-ee3fd5b0c575" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_qlys_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorizedAnnualIncreaseShares_b3c1566c-4add-4310-9f0e-015e724ba946" xlink:href="qlys-20231231.xsd#qlys_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorizedAnnualIncreaseShares"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_c8cfefef-4c5a-4cc2-aa6e-bd2e52f022d9" xlink:to="loc_qlys_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorizedAnnualIncreaseShares_b3c1566c-4add-4310-9f0e-015e724ba946" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_qlys_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorizedAnnualIncreasePercentOfSharesOutstanding_da844cfd-1335-4825-83ae-7ccd3dfdf6a3" xlink:href="qlys-20231231.xsd#qlys_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorizedAnnualIncreasePercentOfSharesOutstanding"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_c8cfefef-4c5a-4cc2-aa6e-bd2e52f022d9" xlink:to="loc_qlys_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorizedAnnualIncreasePercentOfSharesOutstanding_da844cfd-1335-4825-83ae-7ccd3dfdf6a3" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOtherShareIncreaseDecrease_d9422759-7b7b-4d63-b1c0-2da1ac8906a6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOtherShareIncreaseDecrease"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_c8cfefef-4c5a-4cc2-aa6e-bd2e52f022d9" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOtherShareIncreaseDecrease_d9422759-7b7b-4d63-b1c0-2da1ac8906a6" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized_206ac285-e3f0-448e-913c-3d68721b283e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_c8cfefef-4c5a-4cc2-aa6e-bd2e52f022d9" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized_206ac285-e3f0-448e-913c-3d68721b283e" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_606fa09a-1fa2-4605-af40-5fda180b768a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_c8cfefef-4c5a-4cc2-aa6e-bd2e52f022d9" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_606fa09a-1fa2-4605-af40-5fda180b768a" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_eeb73d2e-2855-4e9d-9ed6-d62bfc1d4357" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_c8cfefef-4c5a-4cc2-aa6e-bd2e52f022d9" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_eeb73d2e-2855-4e9d-9ed6-d62bfc1d4357" xlink:type="arc" order="5"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod_e9f692a2-ea8b-415f-b5f3-8e855f82fd50" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_c8cfefef-4c5a-4cc2-aa6e-bd2e52f022d9" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod_e9f692a2-ea8b-415f-b5f3-8e855f82fd50" xlink:type="arc" order="6"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized_c8197b1c-71f4-4de9-ae70-268c201cb3ba" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_c8cfefef-4c5a-4cc2-aa6e-bd2e52f022d9" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized_c8197b1c-71f4-4de9-ae70-268c201cb3ba" xlink:type="arc" order="7"/>
<link:loc xlink:type="locator" xlink:label="loc_qlys_ShareBasedCompensationArrangementByShareBasedPaymentAwardOfferingPeriod_c6b153dd-9be4-473b-accc-e37fb22e3461" xlink:href="qlys-20231231.xsd#qlys_ShareBasedCompensationArrangementByShareBasedPaymentAwardOfferingPeriod"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_c8cfefef-4c5a-4cc2-aa6e-bd2e52f022d9" xlink:to="loc_qlys_ShareBasedCompensationArrangementByShareBasedPaymentAwardOfferingPeriod_c6b153dd-9be4-473b-accc-e37fb22e3461" xlink:type="arc" order="8"/>
<link:loc xlink:type="locator" xlink:label="loc_qlys_EmployeeStockPurchasePlanPercentageOfEligibleCompensationContributable_8a4e4040-2add-47f4-afb6-f953126082f2" xlink:href="qlys-20231231.xsd#qlys_EmployeeStockPurchasePlanPercentageOfEligibleCompensationContributable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_c8cfefef-4c5a-4cc2-aa6e-bd2e52f022d9" xlink:to="loc_qlys_EmployeeStockPurchasePlanPercentageOfEligibleCompensationContributable_8a4e4040-2add-47f4-afb6-f953126082f2" xlink:type="arc" order="9"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercent_31be99da-349b-442a-a22e-6cd516ec09d9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercent"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_c8cfefef-4c5a-4cc2-aa6e-bd2e52f022d9" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercent_31be99da-349b-442a-a22e-6cd516ec09d9" xlink:type="arc" order="10"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans_98d18cb5-dffa-439f-a979-acca15946806" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_c8cfefef-4c5a-4cc2-aa6e-bd2e52f022d9" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans_98d18cb5-dffa-439f-a979-acca15946806" xlink:type="arc" order="11"/>
</link:definitionLink>
<link:roleRef roleURI="http://www.qualys.com/role/StockholdersEquityandStockbasedCompensationSummaryofStockbasedCompensationExpenseDetails" xlink:type="simple" xlink:href="qlys-20231231.xsd#StockholdersEquityandStockbasedCompensationSummaryofStockbasedCompensationExpenseDetails"/>
<link:definitionLink xlink:role="http://www.qualys.com/role/StockholdersEquityandStockbasedCompensationSummaryofStockbasedCompensationExpenseDetails" xlink:type="extended">
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_29610a45-c4b0-4b6f-9232-7958768a884e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_76a8af61-d90b-4c87-90bb-30386bdf08dd" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_29610a45-c4b0-4b6f-9232-7958768a884e" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_76a8af61-d90b-4c87-90bb-30386bdf08dd" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_3a5a10c1-fc02-4588-bcaf-bfe286056009" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementLocationAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_76a8af61-d90b-4c87-90bb-30386bdf08dd" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_3a5a10c1-fc02-4588-bcaf-bfe286056009" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_3a5a10c1-fc02-4588-bcaf-bfe286056009_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementLocationDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_3a5a10c1-fc02-4588-bcaf-bfe286056009" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_3a5a10c1-fc02-4588-bcaf-bfe286056009_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_7df8c842-d7e1-4083-b91d-15101adcb04c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementLocationDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_3a5a10c1-fc02-4588-bcaf-bfe286056009" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_7df8c842-d7e1-4083-b91d-15101adcb04c" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfSalesMember_963cc754-245d-437e-a67f-fd5a23316ae5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CostOfSalesMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_7df8c842-d7e1-4083-b91d-15101adcb04c" xlink:to="loc_us-gaap_CostOfSalesMember_963cc754-245d-437e-a67f-fd5a23316ae5" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResearchAndDevelopmentExpenseMember_d60e636a-5acc-41d0-80cb-942e36be4241" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ResearchAndDevelopmentExpenseMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_7df8c842-d7e1-4083-b91d-15101adcb04c" xlink:to="loc_us-gaap_ResearchAndDevelopmentExpenseMember_d60e636a-5acc-41d0-80cb-942e36be4241" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_SellingAndMarketingExpenseMember_9ec5aa06-6942-49b5-a588-9b960aec0cc3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SellingAndMarketingExpenseMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_7df8c842-d7e1-4083-b91d-15101adcb04c" xlink:to="loc_us-gaap_SellingAndMarketingExpenseMember_9ec5aa06-6942-49b5-a588-9b960aec0cc3" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_GeneralAndAdministrativeExpenseMember_2d9bd5f5-9e00-4d28-aa89-e1207a14618a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GeneralAndAdministrativeExpenseMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_7df8c842-d7e1-4083-b91d-15101adcb04c" xlink:to="loc_us-gaap_GeneralAndAdministrativeExpenseMember_2d9bd5f5-9e00-4d28-aa89-e1207a14618a" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_bb60f425-5d29-4aa1-85c8-ee2856d185e2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AllocatedShareBasedCompensationExpense"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_29610a45-c4b0-4b6f-9232-7958768a884e" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_bb60f425-5d29-4aa1-85c8-ee2856d185e2" xlink:type="arc" order="0"/>
</link:definitionLink>
<link:roleRef roleURI="http://www.qualys.com/role/StockholdersEquityandStockbasedCompensationStockbasedCompensationDetails" xlink:type="simple" xlink:href="qlys-20231231.xsd#StockholdersEquityandStockbasedCompensationStockbasedCompensationDetails"/>
<link:definitionLink xlink:role="http://www.qualys.com/role/StockholdersEquityandStockbasedCompensationStockbasedCompensationDetails" xlink:type="extended">
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_1fa47e13-5081-4308-9afa-fd106ea6e825" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_398de9c3-e0f1-448e-9474-641117fcd1d8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_1fa47e13-5081-4308-9afa-fd106ea6e825" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_398de9c3-e0f1-448e-9474-641117fcd1d8" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_709d2d42-29f8-4f88-b368-b955a710d9d4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AwardTypeAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_398de9c3-e0f1-448e-9474-641117fcd1d8" xlink:to="loc_us-gaap_AwardTypeAxis_709d2d42-29f8-4f88-b368-b955a710d9d4" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_709d2d42-29f8-4f88-b368-b955a710d9d4_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_709d2d42-29f8-4f88-b368-b955a710d9d4" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_709d2d42-29f8-4f88-b368-b955a710d9d4_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_435f4bc6-5a88-4c7f-a59a-a8c2bac3e8bd" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_709d2d42-29f8-4f88-b368-b955a710d9d4" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_435f4bc6-5a88-4c7f-a59a-a8c2bac3e8bd" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockOptionMember_11d6502f-8375-487d-8e48-e8f5d9b7bdc4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EmployeeStockOptionMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_435f4bc6-5a88-4c7f-a59a-a8c2bac3e8bd" xlink:to="loc_us-gaap_EmployeeStockOptionMember_11d6502f-8375-487d-8e48-e8f5d9b7bdc4" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_c9b3e89d-434c-4a95-ace1-c2f8603a84fe" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_435f4bc6-5a88-4c7f-a59a-a8c2bac3e8bd" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_c9b3e89d-434c-4a95-ace1-c2f8603a84fe" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_qlys_PerformanceBasedRestrictedStockUnitsMember_b5093ae7-b850-468e-b66f-800ea07b1ed7" xlink:href="qlys-20231231.xsd#qlys_PerformanceBasedRestrictedStockUnitsMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_435f4bc6-5a88-4c7f-a59a-a8c2bac3e8bd" xlink:to="loc_qlys_PerformanceBasedRestrictedStockUnitsMember_b5093ae7-b850-468e-b66f-800ea07b1ed7" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_qlys_ESPPSharesMember_8ebe43c7-457b-409b-ad99-91e0852f7774" xlink:href="qlys-20231231.xsd#qlys_ESPPSharesMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_435f4bc6-5a88-4c7f-a59a-a8c2bac3e8bd" xlink:to="loc_qlys_ESPPSharesMember_8ebe43c7-457b-409b-ad99-91e0852f7774" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense_0378af47-ef90-4732-afe4-e36dcf652c40" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_1fa47e13-5081-4308-9afa-fd106ea6e825" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense_0378af47-ef90-4732-afe4-e36dcf652c40" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_c64d2619-6ddf-45dd-ba33-8a9b9f809832" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_1fa47e13-5081-4308-9afa-fd106ea6e825" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_c64d2619-6ddf-45dd-ba33-8a9b9f809832" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_ef3dc67a-ceb1-43ab-8a36-39040793972a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_1fa47e13-5081-4308-9afa-fd106ea6e825" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_ef3dc67a-ceb1-43ab-8a36-39040793972a" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_567d8904-9c6b-4a22-9855-916ef4174825" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_1fa47e13-5081-4308-9afa-fd106ea6e825" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_567d8904-9c6b-4a22-9855-916ef4174825" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_qlys_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardPerformancePeriod_a0b36fb6-9474-444f-8bc2-77509c9ee0b4" xlink:href="qlys-20231231.xsd#qlys_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardPerformancePeriod"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_1fa47e13-5081-4308-9afa-fd106ea6e825" xlink:to="loc_qlys_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardPerformancePeriod_a0b36fb6-9474-444f-8bc2-77509c9ee0b4" xlink:type="arc" order="4"/>
</link:definitionLink>
<link:roleRef roleURI="http://www.qualys.com/role/StockholdersEquityandStockbasedCompensationPerformanceBasedStockOptionsandRestrictedStockUnitsDetails" xlink:type="simple" xlink:href="qlys-20231231.xsd#StockholdersEquityandStockbasedCompensationPerformanceBasedStockOptionsandRestrictedStockUnitsDetails"/>
<link:definitionLink xlink:role="http://www.qualys.com/role/StockholdersEquityandStockbasedCompensationPerformanceBasedStockOptionsandRestrictedStockUnitsDetails" xlink:type="extended">
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_f6638f3c-d3c9-48f6-9b73-142f4c5a6e18" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_1edb2178-eb35-4b3f-ae80-2e63401617b7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_f6638f3c-d3c9-48f6-9b73-142f4c5a6e18" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_1edb2178-eb35-4b3f-ae80-2e63401617b7" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_c137d6c5-051a-4038-aab9-fb0adb2988f7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AwardTypeAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_1edb2178-eb35-4b3f-ae80-2e63401617b7" xlink:to="loc_us-gaap_AwardTypeAxis_c137d6c5-051a-4038-aab9-fb0adb2988f7" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_c137d6c5-051a-4038-aab9-fb0adb2988f7_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_c137d6c5-051a-4038-aab9-fb0adb2988f7" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_c137d6c5-051a-4038-aab9-fb0adb2988f7_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_393b0c88-1f22-4c71-99f6-7f6fcbc81883" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_c137d6c5-051a-4038-aab9-fb0adb2988f7" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_393b0c88-1f22-4c71-99f6-7f6fcbc81883" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_819766a7-446a-4ad8-9d7a-2f63454274b1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_393b0c88-1f22-4c71-99f6-7f6fcbc81883" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_819766a7-446a-4ad8-9d7a-2f63454274b1" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockOptionMember_f6199da7-490b-4ac8-8d11-d44168b75a7c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EmployeeStockOptionMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_393b0c88-1f22-4c71-99f6-7f6fcbc81883" xlink:to="loc_us-gaap_EmployeeStockOptionMember_f6199da7-490b-4ac8-8d11-d44168b75a7c" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_qlys_PerformanceBasedRestrictedStockUnitsMember_4908b649-32bb-4aa9-91f2-00845efce804" xlink:href="qlys-20231231.xsd#qlys_PerformanceBasedRestrictedStockUnitsMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_393b0c88-1f22-4c71-99f6-7f6fcbc81883" xlink:to="loc_qlys_PerformanceBasedRestrictedStockUnitsMember_4908b649-32bb-4aa9-91f2-00845efce804" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_VestingAxis_8c9de280-1433-404f-9ca5-963f2bf1c1aa" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_VestingAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_1edb2178-eb35-4b3f-ae80-2e63401617b7" xlink:to="loc_us-gaap_VestingAxis_8c9de280-1433-404f-9ca5-963f2bf1c1aa" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_VestingDomain_8c9de280-1433-404f-9ca5-963f2bf1c1aa_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_VestingDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_VestingAxis_8c9de280-1433-404f-9ca5-963f2bf1c1aa" xlink:to="loc_us-gaap_VestingDomain_8c9de280-1433-404f-9ca5-963f2bf1c1aa_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_VestingDomain_92290e13-0599-4d2e-a9d6-90f10299b07d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_VestingDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_VestingAxis_8c9de280-1433-404f-9ca5-963f2bf1c1aa" xlink:to="loc_us-gaap_VestingDomain_92290e13-0599-4d2e-a9d6-90f10299b07d" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_qlys_TimeBasedSharedBasedCompensationMember_624ecaba-4dc7-4934-a0a8-1e04f2e3bcd3" xlink:href="qlys-20231231.xsd#qlys_TimeBasedSharedBasedCompensationMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VestingDomain_92290e13-0599-4d2e-a9d6-90f10299b07d" xlink:to="loc_qlys_TimeBasedSharedBasedCompensationMember_624ecaba-4dc7-4934-a0a8-1e04f2e3bcd3" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_qlys_PerformanceSharesTrancheThreeMember_ace73ad2-2d3d-42f7-a79b-c5054614c842" xlink:href="qlys-20231231.xsd#qlys_PerformanceSharesTrancheThreeMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VestingDomain_92290e13-0599-4d2e-a9d6-90f10299b07d" xlink:to="loc_qlys_PerformanceSharesTrancheThreeMember_ace73ad2-2d3d-42f7-a79b-c5054614c842" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_79d1813b-497b-4656-81e7-278ecf1faf49" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_1edb2178-eb35-4b3f-ae80-2e63401617b7" xlink:to="loc_srt_RangeAxis_79d1813b-497b-4656-81e7-278ecf1faf49" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_79d1813b-497b-4656-81e7-278ecf1faf49_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_79d1813b-497b-4656-81e7-278ecf1faf49" xlink:to="loc_srt_RangeMember_79d1813b-497b-4656-81e7-278ecf1faf49_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_768671fb-d423-45ac-bfd0-0e2c4be3f5c1" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_79d1813b-497b-4656-81e7-278ecf1faf49" xlink:to="loc_srt_RangeMember_768671fb-d423-45ac-bfd0-0e2c4be3f5c1" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_30ed74f7-fdf3-4e08-aa5a-15f8c6783c28" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MinimumMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_768671fb-d423-45ac-bfd0-0e2c4be3f5c1" xlink:to="loc_srt_MinimumMember_30ed74f7-fdf3-4e08-aa5a-15f8c6783c28" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_1a1371d7-07b7-4ee6-b9fa-490128993e6d" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MaximumMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_768671fb-d423-45ac-bfd0-0e2c4be3f5c1" xlink:to="loc_srt_MaximumMember_1a1371d7-07b7-4ee6-b9fa-490128993e6d" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_TitleOfIndividualAxis_f255342a-2c7b-4f0a-ac34-270d3380f9eb" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_TitleOfIndividualAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_1edb2178-eb35-4b3f-ae80-2e63401617b7" xlink:to="loc_srt_TitleOfIndividualAxis_f255342a-2c7b-4f0a-ac34-270d3380f9eb" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_f255342a-2c7b-4f0a-ac34-270d3380f9eb_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_TitleOfIndividualWithRelationshipToEntityDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_TitleOfIndividualAxis_f255342a-2c7b-4f0a-ac34-270d3380f9eb" xlink:to="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_f255342a-2c7b-4f0a-ac34-270d3380f9eb_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_905a87af-8e9f-41d1-be3a-1914109a2cea" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_TitleOfIndividualWithRelationshipToEntityDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_TitleOfIndividualAxis_f255342a-2c7b-4f0a-ac34-270d3380f9eb" xlink:to="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_905a87af-8e9f-41d1-be3a-1914109a2cea" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_qlys_PresidentAndChiefExecutiveOfficerMember_4dece2a6-d970-4577-813a-c279994b8973" xlink:href="qlys-20231231.xsd#qlys_PresidentAndChiefExecutiveOfficerMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_905a87af-8e9f-41d1-be3a-1914109a2cea" xlink:to="loc_qlys_PresidentAndChiefExecutiveOfficerMember_4dece2a6-d970-4577-813a-c279994b8973" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_ExecutiveOfficerMember_7cc603f8-6efe-48bd-a83a-bdbc06336fd1" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ExecutiveOfficerMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_905a87af-8e9f-41d1-be3a-1914109a2cea" xlink:to="loc_srt_ExecutiveOfficerMember_7cc603f8-6efe-48bd-a83a-bdbc06336fd1" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_34860f23-99fb-4a44-b541-e8b46b7c983a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_f6638f3c-d3c9-48f6-9b73-142f4c5a6e18" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_34860f23-99fb-4a44-b541-e8b46b7c983a" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_qlys_ShareBasedCompensationArrangementByShareBasedPaymentAwardVestingPeriodNumberOfQuarterlyPeriods_c19bb2b2-0a97-4816-9f94-ffa5fb1d4ffd" xlink:href="qlys-20231231.xsd#qlys_ShareBasedCompensationArrangementByShareBasedPaymentAwardVestingPeriodNumberOfQuarterlyPeriods"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_f6638f3c-d3c9-48f6-9b73-142f4c5a6e18" xlink:to="loc_qlys_ShareBasedCompensationArrangementByShareBasedPaymentAwardVestingPeriodNumberOfQuarterlyPeriods_c19bb2b2-0a97-4816-9f94-ffa5fb1d4ffd" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized_2095553e-46ec-4d1f-95ce-c1f5f42f24d3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_f6638f3c-d3c9-48f6-9b73-142f4c5a6e18" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized_2095553e-46ec-4d1f-95ce-c1f5f42f24d3" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_e08b32f9-507b-44f3-97d2-40b954e58363" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_f6638f3c-d3c9-48f6-9b73-142f4c5a6e18" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_e08b32f9-507b-44f3-97d2-40b954e58363" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_qlys_SharebasedCompensationArrangementBySharebasedPaymentAwardTargetPercentage_a8361200-58d0-4e72-a008-8909835160ac" xlink:href="qlys-20231231.xsd#qlys_SharebasedCompensationArrangementBySharebasedPaymentAwardTargetPercentage"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_f6638f3c-d3c9-48f6-9b73-142f4c5a6e18" xlink:to="loc_qlys_SharebasedCompensationArrangementBySharebasedPaymentAwardTargetPercentage_a8361200-58d0-4e72-a008-8909835160ac" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:label="loc_qlys_SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsTargetNumberOfShares_a614c080-8e59-48a0-b994-f1bbbd6b715b" xlink:href="qlys-20231231.xsd#qlys_SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsTargetNumberOfShares"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_f6638f3c-d3c9-48f6-9b73-142f4c5a6e18" xlink:to="loc_qlys_SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsTargetNumberOfShares_a614c080-8e59-48a0-b994-f1bbbd6b715b" xlink:type="arc" order="5"/>
<link:loc xlink:type="locator" xlink:label="loc_qlys_SharebasedCompensationTerminationPeriodTrigger_e8b5f83a-f0a0-44cd-a876-f476e78a869a" xlink:href="qlys-20231231.xsd#qlys_SharebasedCompensationTerminationPeriodTrigger"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_f6638f3c-d3c9-48f6-9b73-142f4c5a6e18" xlink:to="loc_qlys_SharebasedCompensationTerminationPeriodTrigger_e8b5f83a-f0a0-44cd-a876-f476e78a869a" xlink:type="arc" order="6"/>
<link:loc xlink:type="locator" xlink:label="loc_qlys_SharebasedCompensationPercentageOfSharesThatWillVestUponTrigger_d9ce33c8-a212-44b4-ac6b-e82f052d8d80" xlink:href="qlys-20231231.xsd#qlys_SharebasedCompensationPercentageOfSharesThatWillVestUponTrigger"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_f6638f3c-d3c9-48f6-9b73-142f4c5a6e18" xlink:to="loc_qlys_SharebasedCompensationPercentageOfSharesThatWillVestUponTrigger_d9ce33c8-a212-44b4-ac6b-e82f052d8d80" xlink:type="arc" order="7"/>
<link:loc xlink:type="locator" xlink:label="loc_qlys_SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodAsAPercentageOfTarget_46f29900-3a65-4254-97f1-b79db5d999a3" xlink:href="qlys-20231231.xsd#qlys_SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodAsAPercentageOfTarget"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_f6638f3c-d3c9-48f6-9b73-142f4c5a6e18" xlink:to="loc_qlys_SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodAsAPercentageOfTarget_46f29900-3a65-4254-97f1-b79db5d999a3" xlink:type="arc" order="8"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAcceleratedVestingNumber_0b52e5cf-db2e-4a7c-b971-eebbc5fcf210" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAcceleratedVestingNumber"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_f6638f3c-d3c9-48f6-9b73-142f4c5a6e18" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAcceleratedVestingNumber_0b52e5cf-db2e-4a7c-b971-eebbc5fcf210" xlink:type="arc" order="9"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAcceleratedCompensationCost_fbcb6309-17c0-4a6e-a5d5-1f8e7d300a36" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAcceleratedCompensationCost"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_f6638f3c-d3c9-48f6-9b73-142f4c5a6e18" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAcceleratedCompensationCost_fbcb6309-17c0-4a6e-a5d5-1f8e7d300a36" xlink:type="arc" order="10"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_f0e239ee-5f88-4c79-8830-b0dfc1a1956a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_f6638f3c-d3c9-48f6-9b73-142f4c5a6e18" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_f0e239ee-5f88-4c79-8830-b0dfc1a1956a" xlink:type="arc" order="11"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_a0370942-20bc-4180-a63d-93925f82e6ac" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AllocatedShareBasedCompensationExpense"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_f6638f3c-d3c9-48f6-9b73-142f4c5a6e18" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_a0370942-20bc-4180-a63d-93925f82e6ac" xlink:type="arc" order="12"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage_4e21c74b-bcc5-4e69-be71-4ec800646656" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_f6638f3c-d3c9-48f6-9b73-142f4c5a6e18" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage_4e21c74b-bcc5-4e69-be71-4ec800646656" xlink:type="arc" order="13"/>
</link:definitionLink>
<link:roleRef roleURI="http://www.qualys.com/role/StockholdersEquityandStockbasedCompensationFairValueAssumptionsStockOptionsDetails" xlink:type="simple" xlink:href="qlys-20231231.xsd#StockholdersEquityandStockbasedCompensationFairValueAssumptionsStockOptionsDetails"/>
<link:definitionLink xlink:role="http://www.qualys.com/role/StockholdersEquityandStockbasedCompensationFairValueAssumptionsStockOptionsDetails" xlink:type="extended">
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_ee1bf5a5-3b63-4b50-bc37-7c117ca77613" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_a317def1-976e-4b56-8f01-544e6bd50e0a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_ee1bf5a5-3b63-4b50-bc37-7c117ca77613" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_a317def1-976e-4b56-8f01-544e6bd50e0a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_9456a0a6-ebab-4ba4-a177-42a272881293" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_a317def1-976e-4b56-8f01-544e6bd50e0a" xlink:to="loc_srt_RangeAxis_9456a0a6-ebab-4ba4-a177-42a272881293" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_9456a0a6-ebab-4ba4-a177-42a272881293_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_9456a0a6-ebab-4ba4-a177-42a272881293" xlink:to="loc_srt_RangeMember_9456a0a6-ebab-4ba4-a177-42a272881293_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_7dfa2882-a039-4d70-ba64-82afbe2c0dc8" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_9456a0a6-ebab-4ba4-a177-42a272881293" xlink:to="loc_srt_RangeMember_7dfa2882-a039-4d70-ba64-82afbe2c0dc8" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_548e09df-73e0-42fe-8b76-c37f5cb34d61" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MinimumMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_7dfa2882-a039-4d70-ba64-82afbe2c0dc8" xlink:to="loc_srt_MinimumMember_548e09df-73e0-42fe-8b76-c37f5cb34d61" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_5ff825b8-1ee9-494c-a322-1b06cd7ddb65" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MaximumMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_7dfa2882-a039-4d70-ba64-82afbe2c0dc8" xlink:to="loc_srt_MaximumMember_5ff825b8-1ee9-494c-a322-1b06cd7ddb65" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_c983efb1-afdd-4801-a773-cd0309809210" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_ee1bf5a5-3b63-4b50-bc37-7c117ca77613" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_c983efb1-afdd-4801-a773-cd0309809210" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1_71e300fd-2087-4109-82a4-4c99d67ed340" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_ee1bf5a5-3b63-4b50-bc37-7c117ca77613" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1_71e300fd-2087-4109-82a4-4c99d67ed340" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate_2bf188ee-4b8a-455e-b770-e964afd9dc9b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_ee1bf5a5-3b63-4b50-bc37-7c117ca77613" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate_2bf188ee-4b8a-455e-b770-e964afd9dc9b" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate_44ac62d7-bfec-40eb-82c4-8af3ac30a878" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_ee1bf5a5-3b63-4b50-bc37-7c117ca77613" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate_44ac62d7-bfec-40eb-82c4-8af3ac30a878" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate_34840c02-19d1-4e3b-9e6e-6f33cf822fe0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_ee1bf5a5-3b63-4b50-bc37-7c117ca77613" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate_34840c02-19d1-4e3b-9e6e-6f33cf822fe0" xlink:type="arc" order="4"/>
</link:definitionLink>
<link:roleRef roleURI="http://www.qualys.com/role/StockholdersEquityandStockbasedCompensationSummaryofRestrictedStockUnitActivityDetails" xlink:type="simple" xlink:href="qlys-20231231.xsd#StockholdersEquityandStockbasedCompensationSummaryofRestrictedStockUnitActivityDetails"/>
<link:definitionLink xlink:role="http://www.qualys.com/role/StockholdersEquityandStockbasedCompensationSummaryofRestrictedStockUnitActivityDetails" xlink:type="extended">
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_caae413b-0285-41bb-b17a-72f0792cfd85" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_c202cbf9-1005-4d9e-8433-5c9aa45a5e01" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_caae413b-0285-41bb-b17a-72f0792cfd85" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_c202cbf9-1005-4d9e-8433-5c9aa45a5e01" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_bfbdccfe-afc1-4043-b443-9256da468aff" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AwardTypeAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_c202cbf9-1005-4d9e-8433-5c9aa45a5e01" xlink:to="loc_us-gaap_AwardTypeAxis_bfbdccfe-afc1-4043-b443-9256da468aff" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_bfbdccfe-afc1-4043-b443-9256da468aff_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_bfbdccfe-afc1-4043-b443-9256da468aff" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_bfbdccfe-afc1-4043-b443-9256da468aff_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_2ce9cfa8-4671-4e1a-9dbe-40caed04b810" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_bfbdccfe-afc1-4043-b443-9256da468aff" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_2ce9cfa8-4671-4e1a-9dbe-40caed04b810" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_8e297a78-5b97-4034-ab87-124c89e96510" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_2ce9cfa8-4671-4e1a-9dbe-40caed04b810" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_8e297a78-5b97-4034-ab87-124c89e96510" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_qlys_PerformanceBasedRestrictedStockUnitsMember_9406a5f1-0f2e-4e7c-a352-8578ea74c26e" xlink:href="qlys-20231231.xsd#qlys_PerformanceBasedRestrictedStockUnitsMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_2ce9cfa8-4671-4e1a-9dbe-40caed04b810" xlink:to="loc_qlys_PerformanceBasedRestrictedStockUnitsMember_9406a5f1-0f2e-4e7c-a352-8578ea74c26e" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_TitleOfIndividualAxis_90c7a864-d042-4c06-aeaa-9fa55ca552d0" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_TitleOfIndividualAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_c202cbf9-1005-4d9e-8433-5c9aa45a5e01" xlink:to="loc_srt_TitleOfIndividualAxis_90c7a864-d042-4c06-aeaa-9fa55ca552d0" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_90c7a864-d042-4c06-aeaa-9fa55ca552d0_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_TitleOfIndividualWithRelationshipToEntityDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_TitleOfIndividualAxis_90c7a864-d042-4c06-aeaa-9fa55ca552d0" xlink:to="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_90c7a864-d042-4c06-aeaa-9fa55ca552d0_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_d1423b78-bfde-41a3-aacc-aac0fe819d88" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_TitleOfIndividualWithRelationshipToEntityDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_TitleOfIndividualAxis_90c7a864-d042-4c06-aeaa-9fa55ca552d0" xlink:to="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_d1423b78-bfde-41a3-aacc-aac0fe819d88" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_qlys_ExecutiveOfficer1Member_70641618-c350-40dc-ab59-ce1ac6a420d1" xlink:href="qlys-20231231.xsd#qlys_ExecutiveOfficer1Member"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_d1423b78-bfde-41a3-aacc-aac0fe819d88" xlink:to="loc_qlys_ExecutiveOfficer1Member_70641618-c350-40dc-ab59-ce1ac6a420d1" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_ExecutiveOfficerMember_d4d3283e-2daf-45d9-b006-908423f86907" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ExecutiveOfficerMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_d1423b78-bfde-41a3-aacc-aac0fe819d88" xlink:to="loc_srt_ExecutiveOfficerMember_d4d3283e-2daf-45d9-b006-908423f86907" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_qlys_ExecutiveOfficer2Member_2e4f7b9a-31b2-4f4a-a853-c8065b38788e" xlink:href="qlys-20231231.xsd#qlys_ExecutiveOfficer2Member"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_d1423b78-bfde-41a3-aacc-aac0fe819d88" xlink:to="loc_qlys_ExecutiveOfficer2Member_2e4f7b9a-31b2-4f4a-a853-c8065b38788e" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_qlys_ExecutiveOfficer3Member_1ccc97ea-77f0-48fc-838a-ae7df06cc60c" xlink:href="qlys-20231231.xsd#qlys_ExecutiveOfficer3Member"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_d1423b78-bfde-41a3-aacc-aac0fe819d88" xlink:to="loc_qlys_ExecutiveOfficer3Member_1ccc97ea-77f0-48fc-838a-ae7df06cc60c" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_qlys_ExecutiveOfficer4Member_e35fb761-c34d-4c01-910b-16e19b836ead" xlink:href="qlys-20231231.xsd#qlys_ExecutiveOfficer4Member"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_d1423b78-bfde-41a3-aacc-aac0fe819d88" xlink:to="loc_qlys_ExecutiveOfficer4Member_e35fb761-c34d-4c01-910b-16e19b836ead" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_ee2f36eb-efc8-41ab-a365-07e9f3b730eb" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_caae413b-0285-41bb-b17a-72f0792cfd85" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_ee2f36eb-efc8-41ab-a365-07e9f3b730eb" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_ee658ec2-1893-41b8-bb53-cd4bd7db6674" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_ee2f36eb-efc8-41ab-a365-07e9f3b730eb" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_ee658ec2-1893-41b8-bb53-cd4bd7db6674" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_31658827-8c9d-492c-8047-183ecb4d355e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_ee2f36eb-efc8-41ab-a365-07e9f3b730eb" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_31658827-8c9d-492c-8047-183ecb4d355e" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_c880de27-8a24-4990-9138-4d4d0bf6b9dc" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_ee2f36eb-efc8-41ab-a365-07e9f3b730eb" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_c880de27-8a24-4990-9138-4d4d0bf6b9dc" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_40fb6262-eff0-4a92-963b-ff1147f67017" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_ee2f36eb-efc8-41ab-a365-07e9f3b730eb" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_40fb6262-eff0-4a92-963b-ff1147f67017" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_cde76b68-2f9f-4fde-a6c5-942ae2e93a1b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
<link:loc xlink:type="locator" xlink:label="loc_qlys_SharebasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedAndExpectedToVestOutstandingNumber_64d32756-6725-4dad-b06f-9931940b4b6f" xlink:href="qlys-20231231.xsd#qlys_SharebasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedAndExpectedToVestOutstandingNumber"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_caae413b-0285-41bb-b17a-72f0792cfd85" xlink:to="loc_qlys_SharebasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedAndExpectedToVestOutstandingNumber_64d32756-6725-4dad-b06f-9931940b4b6f" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_f18c9929-aa57-4c68-8f5e-482ce06bf228" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_caae413b-0285-41bb-b17a-72f0792cfd85" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_f18c9929-aa57-4c68-8f5e-482ce06bf228" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_0f397f59-9907-481f-ba0c-fe9eaa9efc40" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_f18c9929-aa57-4c68-8f5e-482ce06bf228" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_0f397f59-9907-481f-ba0c-fe9eaa9efc40" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_c17262dd-aa94-455a-bfbf-a603470c3019" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_f18c9929-aa57-4c68-8f5e-482ce06bf228" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_c17262dd-aa94-455a-bfbf-a603470c3019" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_5feabc71-1262-44c8-982e-36c69c383341" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_f18c9929-aa57-4c68-8f5e-482ce06bf228" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_5feabc71-1262-44c8-982e-36c69c383341" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_4ea38ef0-62f9-405c-ae1e-ead4b13aec16" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_f18c9929-aa57-4c68-8f5e-482ce06bf228" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_4ea38ef0-62f9-405c-ae1e-ead4b13aec16" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_c4db998e-5171-4f1e-a583-ac5a724ce4fe" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
<link:loc xlink:type="locator" xlink:label="loc_qlys_SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedAndExpectedToVestOutstandingWeightedAverageExercisePrice_f91868ed-7798-48f2-a7ed-b1b5079c4df5" xlink:href="qlys-20231231.xsd#qlys_SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedAndExpectedToVestOutstandingWeightedAverageExercisePrice"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_caae413b-0285-41bb-b17a-72f0792cfd85" xlink:to="loc_qlys_SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedAndExpectedToVestOutstandingWeightedAverageExercisePrice_f91868ed-7798-48f2-a7ed-b1b5079c4df5" xlink:type="arc" order="3"/>
</link:definitionLink>
<link:roleRef roleURI="http://www.qualys.com/role/StockholdersEquityandStockbasedCompensationNarrativeDetails" xlink:type="simple" xlink:href="qlys-20231231.xsd#StockholdersEquityandStockbasedCompensationNarrativeDetails"/>
<link:definitionLink xlink:role="http://www.qualys.com/role/StockholdersEquityandStockbasedCompensationNarrativeDetails" xlink:type="extended">
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_d116b39b-22d2-45df-96dc-91d14a7337c8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_9fce46d4-58e9-4edd-92be-425245f6df8c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_d116b39b-22d2-45df-96dc-91d14a7337c8" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_9fce46d4-58e9-4edd-92be-425245f6df8c" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_446d7e6a-ed87-4e8c-947f-2a20225910e6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AwardTypeAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_9fce46d4-58e9-4edd-92be-425245f6df8c" xlink:to="loc_us-gaap_AwardTypeAxis_446d7e6a-ed87-4e8c-947f-2a20225910e6" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_446d7e6a-ed87-4e8c-947f-2a20225910e6_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_446d7e6a-ed87-4e8c-947f-2a20225910e6" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_446d7e6a-ed87-4e8c-947f-2a20225910e6_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_a6be0584-a3c4-48d0-9b02-085e698b2373" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_446d7e6a-ed87-4e8c-947f-2a20225910e6" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_a6be0584-a3c4-48d0-9b02-085e698b2373" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_be92d43e-109c-4040-b723-abf05f93fe38" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_a6be0584-a3c4-48d0-9b02-085e698b2373" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_be92d43e-109c-4040-b723-abf05f93fe38" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue_68158b96-bbff-4f1a-b1b4-cd82b4617daa" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_d116b39b-22d2-45df-96dc-91d14a7337c8" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue_68158b96-bbff-4f1a-b1b4-cd82b4617daa" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_qlys_ShareBasedCompensationArrangementByShareBasedPaymentAwardOfferingPeriod_6b12899f-2d7a-4c24-83f8-b6f6458c7a7e" xlink:href="qlys-20231231.xsd#qlys_ShareBasedCompensationArrangementByShareBasedPaymentAwardOfferingPeriod"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_d116b39b-22d2-45df-96dc-91d14a7337c8" xlink:to="loc_qlys_ShareBasedCompensationArrangementByShareBasedPaymentAwardOfferingPeriod_6b12899f-2d7a-4c24-83f8-b6f6458c7a7e" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromExerciseOfStockOptions_3eb851ee-162f-483d-b59c-d2f4908639b4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromExerciseOfStockOptions"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_d116b39b-22d2-45df-96dc-91d14a7337c8" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromExerciseOfStockOptions_3eb851ee-162f-483d-b59c-d2f4908639b4" xlink:type="arc" order="2"/>
</link:definitionLink>
<link:roleRef roleURI="http://www.qualys.com/role/StockholdersEquityandStockbasedCompensationEmployeeStockPurchasePlanValuationAssumptionsDetails" xlink:type="simple" xlink:href="qlys-20231231.xsd#StockholdersEquityandStockbasedCompensationEmployeeStockPurchasePlanValuationAssumptionsDetails"/>
<link:definitionLink xlink:role="http://www.qualys.com/role/StockholdersEquityandStockbasedCompensationEmployeeStockPurchasePlanValuationAssumptionsDetails" xlink:type="extended">
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_348f1551-9b8d-40d8-9bc7-35497a13b457" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_7ae5585b-b521-46f1-8b4b-f35916668dcf" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_348f1551-9b8d-40d8-9bc7-35497a13b457" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_7ae5585b-b521-46f1-8b4b-f35916668dcf" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameAxis_d4550b2f-99fb-4ed2-81e2-1529172dc1c7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PlanNameAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_7ae5585b-b521-46f1-8b4b-f35916668dcf" xlink:to="loc_us-gaap_PlanNameAxis_d4550b2f-99fb-4ed2-81e2-1529172dc1c7" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_d4550b2f-99fb-4ed2-81e2-1529172dc1c7_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PlanNameDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PlanNameAxis_d4550b2f-99fb-4ed2-81e2-1529172dc1c7" xlink:to="loc_us-gaap_PlanNameDomain_d4550b2f-99fb-4ed2-81e2-1529172dc1c7_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_f1d6a899-2f5a-417b-9716-2df52523972f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PlanNameDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PlanNameAxis_d4550b2f-99fb-4ed2-81e2-1529172dc1c7" xlink:to="loc_us-gaap_PlanNameDomain_f1d6a899-2f5a-417b-9716-2df52523972f" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_qlys_The2021EmployeeStockPurchasePlanMember_70881802-872a-4bc7-b8a8-67fe8253e621" xlink:href="qlys-20231231.xsd#qlys_The2021EmployeeStockPurchasePlanMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_f1d6a899-2f5a-417b-9716-2df52523972f" xlink:to="loc_qlys_The2021EmployeeStockPurchasePlanMember_70881802-872a-4bc7-b8a8-67fe8253e621" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_cd1a6a9a-99fa-4416-ae0b-bbf22e72315a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_348f1551-9b8d-40d8-9bc7-35497a13b457" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_cd1a6a9a-99fa-4416-ae0b-bbf22e72315a" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1_7bf04d95-6699-4e0e-b1ac-60f0d56108c2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_348f1551-9b8d-40d8-9bc7-35497a13b457" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1_7bf04d95-6699-4e0e-b1ac-60f0d56108c2" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMinimum_8a04979b-8dec-41c2-9d99-398fee3be45f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMinimum"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_348f1551-9b8d-40d8-9bc7-35497a13b457" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMinimum_8a04979b-8dec-41c2-9d99-398fee3be45f" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMaximum_e6112b05-a320-44b2-8afd-2db83833a466" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMaximum"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_348f1551-9b8d-40d8-9bc7-35497a13b457" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMaximum_e6112b05-a320-44b2-8afd-2db83833a466" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMinimum_4c9e4ed9-e91d-4713-968b-246998622c11" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMinimum"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_348f1551-9b8d-40d8-9bc7-35497a13b457" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMinimum_4c9e4ed9-e91d-4713-968b-246998622c11" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMaximum_691bb6d4-4985-4323-95af-a37a9573e0c8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMaximum"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_348f1551-9b8d-40d8-9bc7-35497a13b457" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMaximum_691bb6d4-4985-4323-95af-a37a9573e0c8" xlink:type="arc" order="5"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate_e30a57cf-6cd5-4d9e-b9bb-382a8490ad9f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_348f1551-9b8d-40d8-9bc7-35497a13b457" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate_e30a57cf-6cd5-4d9e-b9bb-382a8490ad9f" xlink:type="arc" order="6"/>
</link:definitionLink>
<link:roleRef roleURI="http://www.qualys.com/role/StockholdersEquityandStockbasedCompensationShareRepurchaseProgramDetails" xlink:type="simple" xlink:href="qlys-20231231.xsd#StockholdersEquityandStockbasedCompensationShareRepurchaseProgramDetails"/>
<link:definitionLink xlink:role="http://www.qualys.com/role/StockholdersEquityandStockbasedCompensationShareRepurchaseProgramDetails" xlink:type="extended">
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_67861f47-f4ff-432e-ab65-ea60799dcdd1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_bbe5679c-1748-480c-a386-187b98eb26a5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_67861f47-f4ff-432e-ab65-ea60799dcdd1" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_bbe5679c-1748-480c-a386-187b98eb26a5" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_3c289ebe-73dc-47f5-86c5-749d2e3ccbad" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SubsequentEventTypeAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_bbe5679c-1748-480c-a386-187b98eb26a5" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_3c289ebe-73dc-47f5-86c5-749d2e3ccbad" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_3c289ebe-73dc-47f5-86c5-749d2e3ccbad_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SubsequentEventTypeDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_3c289ebe-73dc-47f5-86c5-749d2e3ccbad" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_3c289ebe-73dc-47f5-86c5-749d2e3ccbad_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_14073608-def8-4d72-9e14-5376c884e43b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SubsequentEventTypeDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_3c289ebe-73dc-47f5-86c5-749d2e3ccbad" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_14073608-def8-4d72-9e14-5376c884e43b" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember_80b16d3b-94e7-4004-bbfe-d786cfeedc4f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SubsequentEventMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_14073608-def8-4d72-9e14-5376c884e43b" xlink:to="loc_us-gaap_SubsequentEventMember_80b16d3b-94e7-4004-bbfe-d786cfeedc4f" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_qlys_StockRepurchaseProgramAdditionalAuthorizedAmount_93d59ca1-9e23-481c-acd5-58de680727bb" xlink:href="qlys-20231231.xsd#qlys_StockRepurchaseProgramAdditionalAuthorizedAmount"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_67861f47-f4ff-432e-ab65-ea60799dcdd1" xlink:to="loc_qlys_StockRepurchaseProgramAdditionalAuthorizedAmount_93d59ca1-9e23-481c-acd5-58de680727bb" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchaseProgramAuthorizedAmount1_2f2bdbbe-3a43-4f4e-b23d-929edc3de292" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockRepurchaseProgramAuthorizedAmount1"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_67861f47-f4ff-432e-ab65-ea60799dcdd1" xlink:to="loc_us-gaap_StockRepurchaseProgramAuthorizedAmount1_2f2bdbbe-3a43-4f4e-b23d-929edc3de292" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchasedAndRetiredDuringPeriodShares_a36bbe51-dcfc-4028-a5ae-b2e9f0c90623" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockRepurchasedAndRetiredDuringPeriodShares"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_67861f47-f4ff-432e-ab65-ea60799dcdd1" xlink:to="loc_us-gaap_StockRepurchasedAndRetiredDuringPeriodShares_a36bbe51-dcfc-4028-a5ae-b2e9f0c90623" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchasedAndRetiredDuringPeriodValue_18744a53-6d76-4e79-baf5-6bf1b38db738" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockRepurchasedAndRetiredDuringPeriodValue"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_67861f47-f4ff-432e-ab65-ea60799dcdd1" xlink:to="loc_us-gaap_StockRepurchasedAndRetiredDuringPeriodValue_18744a53-6d76-4e79-baf5-6bf1b38db738" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1_a4a6e84d-1971-4407-b639-d850ca7a532d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_67861f47-f4ff-432e-ab65-ea60799dcdd1" xlink:to="loc_us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1_a4a6e84d-1971-4407-b639-d850ca7a532d" xlink:type="arc" order="4"/>
</link:definitionLink>
<link:roleRef roleURI="http://www.qualys.com/role/IncomeTaxesNarrativeDetails" xlink:type="simple" xlink:href="qlys-20231231.xsd#IncomeTaxesNarrativeDetails"/>
<link:definitionLink xlink:role="http://www.qualys.com/role/IncomeTaxesNarrativeDetails" xlink:type="extended">
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxContingencyLineItems_71edd982-8e64-46e5-a883-37c09b4a4b9e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeTaxContingencyLineItems"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxContingencyTable_9d4b0c54-aa75-4613-ac85-cb7e3880010f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeTaxContingencyTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_IncomeTaxContingencyLineItems_71edd982-8e64-46e5-a883-37c09b4a4b9e" xlink:to="loc_us-gaap_IncomeTaxContingencyTable_9d4b0c54-aa75-4613-ac85-cb7e3880010f" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxAuthorityAxis_7f6cd6cc-69ba-45e2-afb6-c2907dcc0cde" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeTaxAuthorityAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeTaxContingencyTable_9d4b0c54-aa75-4613-ac85-cb7e3880010f" xlink:to="loc_us-gaap_IncomeTaxAuthorityAxis_7f6cd6cc-69ba-45e2-afb6-c2907dcc0cde" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxAuthorityDomain_7f6cd6cc-69ba-45e2-afb6-c2907dcc0cde_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeTaxAuthorityDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeTaxAuthorityAxis_7f6cd6cc-69ba-45e2-afb6-c2907dcc0cde" xlink:to="loc_us-gaap_IncomeTaxAuthorityDomain_7f6cd6cc-69ba-45e2-afb6-c2907dcc0cde_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxAuthorityDomain_99a3d707-c8e9-4f6e-8131-d528d9cc5456" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeTaxAuthorityDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeTaxAuthorityAxis_7f6cd6cc-69ba-45e2-afb6-c2907dcc0cde" xlink:to="loc_us-gaap_IncomeTaxAuthorityDomain_99a3d707-c8e9-4f6e-8131-d528d9cc5456" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignCountryMember_0222697d-9503-4fab-ad8d-89040d39b4cc" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ForeignCountryMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxAuthorityDomain_99a3d707-c8e9-4f6e-8131-d528d9cc5456" xlink:to="loc_us-gaap_ForeignCountryMember_0222697d-9503-4fab-ad8d-89040d39b4cc" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredTaxAssetsValuationAllowance_a82bfb2c-d743-4d87-9562-7331eec875d4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DeferredTaxAssetsValuationAllowance"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxContingencyLineItems_71edd982-8e64-46e5-a883-37c09b4a4b9e" xlink:to="loc_us-gaap_DeferredTaxAssetsValuationAllowance_a82bfb2c-d743-4d87-9562-7331eec875d4" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLossCarryforwards_cf92bd37-1235-4cb3-9656-7a94c9559879" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OperatingLossCarryforwards"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxContingencyLineItems_71edd982-8e64-46e5-a883-37c09b4a4b9e" xlink:to="loc_us-gaap_OperatingLossCarryforwards_cf92bd37-1235-4cb3-9656-7a94c9559879" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_TaxCreditCarryforwardAmount_8a3c4352-82a3-4b5e-a5d5-e772e706729a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TaxCreditCarryforwardAmount"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxContingencyLineItems_71edd982-8e64-46e5-a883-37c09b4a4b9e" xlink:to="loc_us-gaap_TaxCreditCarryforwardAmount_8a3c4352-82a3-4b5e-a5d5-e772e706729a" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate_cbf9c910-e7c1-4b0e-a747-d920ca8c12e0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxContingencyLineItems_71edd982-8e64-46e5-a883-37c09b4a4b9e" xlink:to="loc_us-gaap_UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate_cbf9c910-e7c1-4b0e-a747-d920ca8c12e0" xlink:type="arc" order="3"/>
</link:definitionLink>
<link:roleRef roleURI="http://www.qualys.com/role/SegmentandGeographicAreaInformationRevenueandPropertyandEquipmentNetbyGeographicAreaDetails" xlink:type="simple" xlink:href="qlys-20231231.xsd#SegmentandGeographicAreaInformationRevenueandPropertyandEquipmentNetbyGeographicAreaDetails"/>
<link:definitionLink xlink:role="http://www.qualys.com/role/SegmentandGeographicAreaInformationRevenueandPropertyandEquipmentNetbyGeographicAreaDetails" xlink:type="extended">
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_719c0aeb-2156-496b-97ad-76007bb7c43a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SegmentReportingInformationLineItems"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_20ddc702-186e-40a7-948b-cb8f1226c174" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_719c0aeb-2156-496b-97ad-76007bb7c43a" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_20ddc702-186e-40a7-948b-cb8f1226c174" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_f944feeb-1fa1-4d13-949b-a9e45f313c5a" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_StatementGeographicalAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_20ddc702-186e-40a7-948b-cb8f1226c174" xlink:to="loc_srt_StatementGeographicalAxis_f944feeb-1fa1-4d13-949b-a9e45f313c5a" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_f944feeb-1fa1-4d13-949b-a9e45f313c5a_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_SegmentGeographicalDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_f944feeb-1fa1-4d13-949b-a9e45f313c5a" xlink:to="loc_srt_SegmentGeographicalDomain_f944feeb-1fa1-4d13-949b-a9e45f313c5a_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_cc3772ba-27f4-445e-9a74-74f0ae313dea" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_SegmentGeographicalDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_f944feeb-1fa1-4d13-949b-a9e45f313c5a" xlink:to="loc_srt_SegmentGeographicalDomain_cc3772ba-27f4-445e-9a74-74f0ae313dea" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_country_US_6cf10fbf-ef39-460d-a33a-4be680b93b68" xlink:href="https://xbrl.sec.gov/country/2023/country-2023.xsd#country_US"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_cc3772ba-27f4-445e-9a74-74f0ae313dea" xlink:to="loc_country_US_6cf10fbf-ef39-460d-a33a-4be680b93b68" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonUsMember_7f22cf63-8dfe-4d7b-bcc5-2d1a9daaabe7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NonUsMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_cc3772ba-27f4-445e-9a74-74f0ae313dea" xlink:to="loc_us-gaap_NonUsMember_7f22cf63-8dfe-4d7b-bcc5-2d1a9daaabe7" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_country_IN_16fe7aca-c626-4e36-af29-9a785296a323" xlink:href="https://xbrl.sec.gov/country/2023/country-2023.xsd#country_IN"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_cc3772ba-27f4-445e-9a74-74f0ae313dea" xlink:to="loc_country_IN_16fe7aca-c626-4e36-af29-9a785296a323" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_qlys_OtherGeographicAreasMember_a0f3185b-7d6f-467e-930e-c930db299580" xlink:href="qlys-20231231.xsd#qlys_OtherGeographicAreasMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_cc3772ba-27f4-445e-9a74-74f0ae313dea" xlink:to="loc_qlys_OtherGeographicAreasMember_a0f3185b-7d6f-467e-930e-c930db299580" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_48e37759-67d1-4d46-8299-c70513650dbe" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_719c0aeb-2156-496b-97ad-76007bb7c43a" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_48e37759-67d1-4d46-8299-c70513650dbe" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_qlys_PropertyPlantAndEquipmentAndOperatingLeaseRightofuseAssets_ccf719fa-7e10-451b-b70a-d72cf793ce96" xlink:href="qlys-20231231.xsd#qlys_PropertyPlantAndEquipmentAndOperatingLeaseRightofuseAssets"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_719c0aeb-2156-496b-97ad-76007bb7c43a" xlink:to="loc_qlys_PropertyPlantAndEquipmentAndOperatingLeaseRightofuseAssets_ccf719fa-7e10-451b-b70a-d72cf793ce96" xlink:type="arc" order="1"/>
</link:definitionLink>
<link:roleRef roleURI="http://www.qualys.com/role/NetIncomePerShareAntidilutiveNetIncomePerShareDetails" xlink:type="simple" xlink:href="qlys-20231231.xsd#NetIncomePerShareAntidilutiveNetIncomePerShareDetails"/>
<link:definitionLink xlink:role="http://www.qualys.com/role/NetIncomePerShareAntidilutiveNetIncomePerShareDetails" xlink:type="extended">
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_972076e9-d220-48df-bd0b-0be6c29596f4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_855f1527-14ae-4d68-96e8-d10732c93162" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_972076e9-d220-48df-bd0b-0be6c29596f4" xlink:to="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_855f1527-14ae-4d68-96e8-d10732c93162" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_8f00708e-bffb-437a-af0d-3f7b04ae87af" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_855f1527-14ae-4d68-96e8-d10732c93162" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_8f00708e-bffb-437a-af0d-3f7b04ae87af" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_8f00708e-bffb-437a-af0d-3f7b04ae87af_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AntidilutiveSecuritiesNameDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_8f00708e-bffb-437a-af0d-3f7b04ae87af" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_8f00708e-bffb-437a-af0d-3f7b04ae87af_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_4fe63969-572c-4fdf-b47d-8a7866fe5928" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AntidilutiveSecuritiesNameDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_8f00708e-bffb-437a-af0d-3f7b04ae87af" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_4fe63969-572c-4fdf-b47d-8a7866fe5928" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockOptionMember_74b6c569-6875-482a-9170-24ea71a538d8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EmployeeStockOptionMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_4fe63969-572c-4fdf-b47d-8a7866fe5928" xlink:to="loc_us-gaap_EmployeeStockOptionMember_74b6c569-6875-482a-9170-24ea71a538d8" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_53e5d251-490f-4307-acfd-771661ee5a75" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_4fe63969-572c-4fdf-b47d-8a7866fe5928" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_53e5d251-490f-4307-acfd-771661ee5a75" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_qlys_EmployeeStockPurchasePlanSharesMember_1e264345-a767-4360-9104-e9a47baebce8" xlink:href="qlys-20231231.xsd#qlys_EmployeeStockPurchasePlanSharesMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_4fe63969-572c-4fdf-b47d-8a7866fe5928" xlink:to="loc_qlys_EmployeeStockPurchasePlanSharesMember_1e264345-a767-4360-9104-e9a47baebce8" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_7a9f593f-a100-4493-92d3-c7b18e423734" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_972076e9-d220-48df-bd0b-0be6c29596f4" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_7a9f593f-a100-4493-92d3-c7b18e423734" xlink:type="arc" order="0"/>
</link:definitionLink>
<link:roleRef roleURI="http://xbrl.sec.gov/ecd/AwardTypeOnly" xlink:type="simple" xlink:href="https://xbrl.sec.gov/ecd/2023/ecd-2023.xsd#AwardTypeOnly"/>
<link:definitionLink xlink:role="http://xbrl.sec.gov/ecd/AwardTypeOnly" xlink:type="extended">
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:label="loc_qlys_PerformanceBasedRestrictedStockUnitsMember_176f40ca-6164-4fc8-852a-b24f3340e6ce" xlink:href="qlys-20231231.xsd#qlys_PerformanceBasedRestrictedStockUnitsMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:to="loc_qlys_PerformanceBasedRestrictedStockUnitsMember_176f40ca-6164-4fc8-852a-b24f3340e6ce" xlink:type="arc" order="5"/>
<link:loc xlink:type="locator" xlink:label="loc_qlys_ESPPSharesMember_b0835af7-626e-450b-82ef-3bf76dd99e45" xlink:href="qlys-20231231.xsd#qlys_ESPPSharesMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:to="loc_qlys_ESPPSharesMember_b0835af7-626e-450b-82ef-3bf76dd99e45" xlink:type="arc" order="6"/>
</link:definitionLink>
<link:roleRef roleURI="http://xbrl.sec.gov/ecd/role/IndividualsOnly" xlink:type="simple" xlink:href="https://xbrl.sec.gov/ecd/2023/ecd-2023.xsd#IndividualsOnly"/>
<link:definitionLink xlink:role="http://xbrl.sec.gov/ecd/role/IndividualsOnly" xlink:type="extended">
<link:loc xlink:type="locator" xlink:label="loc_ecd_AllIndividualsMember" xlink:href="https://xbrl.sec.gov/ecd/2023/ecd-2023.xsd#ecd_AllIndividualsMember"/>
<link:loc xlink:type="locator" xlink:label="loc_qlys_JeffreyHankMember_a8562b16-c886-4a21-bca6-7f1b1f20a700" xlink:href="qlys-20231231.xsd#qlys_JeffreyHankMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ecd_AllIndividualsMember" xlink:to="loc_qlys_JeffreyHankMember_a8562b16-c886-4a21-bca6-7f1b1f20a700" xlink:type="arc" order="2"/>
</link:definitionLink>
</link:linkbase>


11 Previous Filings that this Filing References

  As Of               Filer                 Filing    For·On·As Docs:Size             Issuer                      Filing Agent

11/02/22  Qualys, Inc.                      8-K:2,5,9  10/27/22   12:588K                                   Donnelley … Solutions/FA
 6/10/22  Qualys, Inc.                      8-K:5,9     6/08/22   11:259K                                   Donnelley … Solutions/FA
 2/22/22  Qualys, Inc.                      10-K       12/31/21   98:10M                                    RDG Filings/FA
 6/11/21  Qualys, Inc.                      8-K:5,9     6/09/21   11:233K                                   Donnelley … Solutions/FA
 5/26/20  Qualys, Inc.                      8-K:5,9     5/21/20   12:186K                                   Donnelley … Solutions/FA
 2/21/20  Qualys, Inc.                      10-K       12/31/19   98:13M                                    Workiva Inc Wde… FA01/FA
10/19/16  Qualys, Inc.                      8-K:1,2,9  10/14/16    2:2.3M                                   Donnelley … Solutions/FA
 4/25/16  Qualys, Inc.                      DEF 14A     6/06/16    1:1.1M                                   Donnelley … Solutions/FA
 9/12/12  Qualys, Inc.                      S-1/A¶                15:6.8M                                   Donnelley … Solutions/FA
 8/10/12  Qualys, Inc.                      S-1/A¶                 6:4.5M                                   Donnelley … Solutions/FA
 6/08/12  Qualys, Inc.                      S-1                   18:7.2M                                   Donnelley … Solutions/FA
Top
Filing Submission 0001107843-24-000008   –   Alternative Formats (Word / Rich Text, HTML, Plain Text, et al.)

Copyright © 2024 Fran Finnegan & Company LLC – All Rights Reserved.
AboutPrivacyRedactionsHelp — Tue., May 14, 1:46:44.2am ET