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<?xml version="1.0" encoding="windows-1252"?> |
<ownershipDocument> |
| <schemaVersion> X0306 </schemaVersion> |
| <documentType> 4 </documentType> |
| <periodOfReport> 2020-03-13 </periodOfReport> |
| <notSubjectToSection16> 0 </notSubjectToSection16> |
| <issuer> |
| | <issuerCik> 0001057352 </issuerCik> |
| | <issuerName> COSTAR GROUP, INC. </issuerName> |
| | <issuerTradingSymbol> CSGP </issuerTradingSymbol> |
| | </issuer> |
| <reportingOwner> |
| | <reportingOwnerId> |
| | | <rptOwnerCik> 0001717178 </rptOwnerCik> |
| | | <rptOwnerName> Ruggles Lisa </rptOwnerName> |
| | | </reportingOwnerId> |
| | <reportingOwnerAddress> |
| | | <rptOwnerStreet1> C/O COSTAR GROUP, INC. </rptOwnerStreet1> |
| | | <rptOwnerStreet2> 1331 L STREET, NW </rptOwnerStreet2> |
| | | <rptOwnerCity> WASHINGTON </rptOwnerCity> |
| | | <rptOwnerState> DC </rptOwnerState> |
| | | <rptOwnerZipCode> 20005 </rptOwnerZipCode> |
| | | <rptOwnerStateDescription></rptOwnerStateDescription> |
| | | </reportingOwnerAddress> |
| | <reportingOwnerRelationship> |
| | | <isDirector> 0 </isDirector> |
| | | <isOfficer> 1 </isOfficer> |
| | | <isTenPercentOwner> 0 </isTenPercentOwner> |
| | | <isOther> 0 </isOther> |
| | | <officerTitle> Senior VP, Global Research </officerTitle> |
| | | <otherText></otherText> |
| | | </reportingOwnerRelationship> |
| | </reportingOwner> |
| <nonDerivativeTable> |
| | <nonDerivativeTransaction> |
| | | <securityTitle> |
| <value> Common Stock, par value $0.01 per share </value> |
| </securityTitle> |
| | | <transactionDate> |
| <value> 2020-03-13 </value> |
| </transactionDate> |
| | | <transactionCoding> |
| <transactionFormType> 4 </transactionFormType> |
| <transactionCode> A </transactionCode> |
| <equitySwapInvolved> 0 </equitySwapInvolved> |
| </transactionCoding> |
| | | <transactionAmounts> |
| <transactionShares> |
| <value> 152 </value> |
| </transactionShares> |
| <transactionPricePerShare> |
| <footnoteId id="F1"/> |
| </transactionPricePerShare> |
| <transactionAcquiredDisposedCode> |
| <value> A </value> |
| </transactionAcquiredDisposedCode> |
| </transactionAmounts> |
| | | <postTransactionAmounts> |
| <sharesOwnedFollowingTransaction> |
| <value> 18029 </value> |
| <footnoteId id="F2"/> |
| </sharesOwnedFollowingTransaction> |
| </postTransactionAmounts> |
| | | <ownershipNature> |
| <directOrIndirectOwnership> |
| <value> D </value> |
| </directOrIndirectOwnership> |
| </ownershipNature> |
| | | </nonDerivativeTransaction> |
| | </nonDerivativeTable> |
| <derivativeTable></derivativeTable> |
| <footnotes> |
| | <footnote id="F1"> Pursuant to the Management Stock Purchase Plan, all or a portion of the reporting person's annual cash incentive amount was converted to Deferred Stock Units (each equivalent to one share of common stock) at $663.93 per unit, and the Company awarded the reporting person Restricted Stock Units that vest in full after four years for an equal number of shares of common stock. </footnote> |
| | <footnote id="F2"> Represents all shares of Common Stock owned, consisting of 2,934 shares of Common Stock and 14,377 shares of Common Stock subject to unvested Restricted Stock grants, 359 shares of Deferred Stock Units and 359 shares of unvested Restricted Stock Units. </footnote> |
| | </footnotes> |
| <remarks></remarks> |
| <ownerSignature> |
| | <signatureName> /s/ Jeannette Koonce, Attorney-in-Fact </signatureName> |
| | <signatureDate> 2020-03-16 </signatureDate> |
| | </ownerSignature> |
| </ownershipDocument> |