<?xml version="1.0" encoding="UTF-8"?>

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2026 Workiva-->
<!--r:019ebcb9-068c-73b6-b0b9-a0411a3ed2ba,g:e22679ec-0eac-42c2-a54c-b4fbfa9eb33e-->
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:csgp="http://www.costar.com/20260630" xmlns:xbrli="http://www.xbrl.org/2003/instance" xmlns:dtr-types="http://www.xbrl.org/dtr/type/2024-01-31" attributeFormDefault="unqualified" elementFormDefault="qualified" targetNamespace="http://www.costar.com/20260630">
  <xs:import namespace="http://fasb.org/srt/2026" schemaLocation="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd"/>
  <xs:import namespace="http://fasb.org/us-gaap/2026" schemaLocation="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd"/>
  <xs:import namespace="http://www.xbrl.org/2003/instance" schemaLocation="http://www.xbrl.org/2003/xbrl-instance-2003-12-31.xsd"/>
  <xs:import namespace="http://www.xbrl.org/2003/linkbase" schemaLocation="http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd"/>
  <xs:import namespace="http://www.xbrl.org/dtr/type/2024-01-31" schemaLocation="https://www.xbrl.org/dtr/type/2024-01-31/types.xsd"/>
  <xs:import namespace="http://xbrl.sec.gov/dei/2026" schemaLocation="https://xbrl.sec.gov/dei/2026/dei-2026.xsd"/>
  <xs:import namespace="http://xbrl.sec.gov/ecd/2026" schemaLocation="https://xbrl.sec.gov/ecd/2026/ecd-2026.xsd"/>
  <xs:annotation>
    <xs:appinfo>
      <link:linkbaseRef xmlns:xlink="http://www.w3.org/1999/xlink" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:href="csgp-20260630_pre.xml" xlink:role="http://www.xbrl.org/2003/role/presentationLinkbaseRef" xlink:type="simple"/>
      <link:linkbaseRef xmlns:xlink="http://www.w3.org/1999/xlink" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:href="csgp-20260630_def.xml" xlink:role="http://www.xbrl.org/2003/role/definitionLinkbaseRef" xlink:type="simple"/>
      <link:linkbaseRef xmlns:xlink="http://www.w3.org/1999/xlink" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:href="csgp-20260630_lab.xml" xlink:role="http://www.xbrl.org/2003/role/labelLinkbaseRef" xlink:type="simple"/>
      <link:linkbaseRef xmlns:xlink="http://www.w3.org/1999/xlink" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:href="csgp-20260630_cal.xml" xlink:role="http://www.xbrl.org/2003/role/calculationLinkbaseRef" xlink:type="simple"/>
      <link:roleType id="Coverpage" roleURI="http://www.costar.com/role/Coverpage">
        <link:definition>0000001 - Document - Cover page</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CONDENSEDCONSOLIDATEDSTATEMENTSOFOPERATIONS" roleURI="http://www.costar.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFOPERATIONS">
        <link:definition>9952151 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CONDENSEDCONSOLIDATEDSTATEMENTSOFCOMPREHENSIVEINCOME" roleURI="http://www.costar.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFCOMPREHENSIVEINCOME">
        <link:definition>9952152 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CONDENSEDCONSOLIDATEDBALANCESHEETS" roleURI="http://www.costar.com/role/CONDENSEDCONSOLIDATEDBALANCESHEETS">
        <link:definition>9952153 - Statement - CONDENSED CONSOLIDATED BALANCE SHEETS</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CONDENSEDCONSOLIDATEDSTATEMENTSOFCHANGESINSTOCKHOLDERSEQUITY" roleURI="http://www.costar.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFCHANGESINSTOCKHOLDERSEQUITY">
        <link:definition>9952154 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS&#8217; EQUITY</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CONDENSEDCONSOLIDATEDSTATEMENTSOFCASHFLOWS" roleURI="http://www.costar.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFCASHFLOWS">
        <link:definition>9952155 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="ORGANIZATION" roleURI="http://www.costar.com/role/ORGANIZATION">
        <link:definition>9952156 - Disclosure - ORGANIZATION</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIES" roleURI="http://www.costar.com/role/SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIES">
        <link:definition>9952157 - Disclosure - SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="REVENUEFROMCONTRACTSWITHCUSTOMERS" roleURI="http://www.costar.com/role/REVENUEFROMCONTRACTSWITHCUSTOMERS">
        <link:definition>9952158 - Disclosure - REVENUE FROM CONTRACTS WITH CUSTOMERS</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="ACQUISITIONS" roleURI="http://www.costar.com/role/ACQUISITIONS">
        <link:definition>9952159 - Disclosure - ACQUISITIONS</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="INVESTMENTSANDFAIRVALUEMEASUREMENTS" roleURI="http://www.costar.com/role/INVESTMENTSANDFAIRVALUEMEASUREMENTS">
        <link:definition>9952160 - Disclosure - INVESTMENTS AND FAIR VALUE MEASUREMENTS</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="LEASES" roleURI="http://www.costar.com/role/LEASES">
        <link:definition>9952161 - Disclosure - LEASES</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="GOODWILL" roleURI="http://www.costar.com/role/GOODWILL">
        <link:definition>9952162 - Disclosure - GOODWILL</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="INTANGIBLEASSETS" roleURI="http://www.costar.com/role/INTANGIBLEASSETS">
        <link:definition>9952163 - Disclosure - INTANGIBLE ASSETS</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="LONGTERMDEBT" roleURI="http://www.costar.com/role/LONGTERMDEBT">
        <link:definition>9952164 - Disclosure - LONG-TERM DEBT</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="INCOMETAXES" roleURI="http://www.costar.com/role/INCOMETAXES">
        <link:definition>9952165 - Disclosure - INCOME TAXES</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="COMMITMENTSANDCONTINGENCIES" roleURI="http://www.costar.com/role/COMMITMENTSANDCONTINGENCIES">
        <link:definition>9952166 - Disclosure - COMMITMENTS AND CONTINGENCIES</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="SEGMENTREPORTING" roleURI="http://www.costar.com/role/SEGMENTREPORTING">
        <link:definition>9952167 - Disclosure - SEGMENT REPORTING</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="STOCKHOLDERSEQUITY" roleURI="http://www.costar.com/role/STOCKHOLDERSEQUITY">
        <link:definition>9952168 - Disclosure - STOCKHOLDERS' EQUITY</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="EMPLOYEEBENEFITPLANS" roleURI="http://www.costar.com/role/EMPLOYEEBENEFITPLANS">
        <link:definition>9952169 - Disclosure - EMPLOYEE BENEFIT PLANS</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="SUBSEQUENTEVENTS" roleURI="http://www.costar.com/role/SUBSEQUENTEVENTS">
        <link:definition>9952170 - Disclosure - SUBSEQUENT EVENTS</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESPolicies" roleURI="http://www.costar.com/role/SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESPolicies">
        <link:definition>9955511 - Disclosure - SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESTables" roleURI="http://www.costar.com/role/SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESTables">
        <link:definition>9955512 - Disclosure - SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="REVENUEFROMCONTRACTSWITHCUSTOMERSTables" roleURI="http://www.costar.com/role/REVENUEFROMCONTRACTSWITHCUSTOMERSTables">
        <link:definition>9955513 - Disclosure - REVENUE FROM CONTRACTS WITH CUSTOMERS (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="ACQUISITIONSTables" roleURI="http://www.costar.com/role/ACQUISITIONSTables">
        <link:definition>9955514 - Disclosure - ACQUISITIONS (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="LEASESTables" roleURI="http://www.costar.com/role/LEASESTables">
        <link:definition>9955515 - Disclosure - LEASES (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="GOODWILLTables" roleURI="http://www.costar.com/role/GOODWILLTables">
        <link:definition>9955516 - Disclosure - GOODWILL (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="INTANGIBLEASSETSTables" roleURI="http://www.costar.com/role/INTANGIBLEASSETSTables">
        <link:definition>9955517 - Disclosure - INTANGIBLE ASSETS (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="LONGTERMDEBTTables" roleURI="http://www.costar.com/role/LONGTERMDEBTTables">
        <link:definition>9955518 - Disclosure - LONG-TERM DEBT (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="COMMITMENTSANDCONTINGENCIESTables" roleURI="http://www.costar.com/role/COMMITMENTSANDCONTINGENCIESTables">
        <link:definition>9955519 - Disclosure - COMMITMENTS AND CONTINGENCIES (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="SEGMENTREPORTINGTables" roleURI="http://www.costar.com/role/SEGMENTREPORTINGTables">
        <link:definition>9955520 - Disclosure - SEGMENT REPORTING (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="EMPLOYEEBENEFITPLANSTables" roleURI="http://www.costar.com/role/EMPLOYEEBENEFITPLANSTables">
        <link:definition>9955521 - Disclosure - EMPLOYEE BENEFIT PLANS (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="ORGANIZATIONDetails" roleURI="http://www.costar.com/role/ORGANIZATIONDetails">
        <link:definition>9955522 - Disclosure - ORGANIZATION (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESPrinciplesofConsolidationDetails" roleURI="http://www.costar.com/role/SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESPrinciplesofConsolidationDetails">
        <link:definition>9955523 - Disclosure - SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Principles of Consolidation (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESRevenueRecognitionDetails" roleURI="http://www.costar.com/role/SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESRevenueRecognitionDetails">
        <link:definition>9955524 - Disclosure - SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Revenue Recognition (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESForeignCurrencyTranslationandAccumulatedOtherComprehensiveIncomeDetails" roleURI="http://www.costar.com/role/SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESForeignCurrencyTranslationandAccumulatedOtherComprehensiveIncomeDetails">
        <link:definition>9955525 - Disclosure - SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Foreign Currency Translation and Accumulated Other Comprehensive Income (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESScheduleofCalculationofBasicandDilutedEarningsPerShareDetails" roleURI="http://www.costar.com/role/SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESScheduleofCalculationofBasicandDilutedEarningsPerShareDetails">
        <link:definition>9955526 - Disclosure - SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Schedule of Calculation of Basic and Diluted Earnings Per Share (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESScheduleofAntidilutiveSecuritiesExcludedfromComputationofEarningsPerShareDetails" roleURI="http://www.costar.com/role/SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESScheduleofAntidilutiveSecuritiesExcludedfromComputationofEarningsPerShareDetails">
        <link:definition>9955527 - Disclosure - SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Schedule of Anti-dilutive Securities Excluded from Computation of Earnings Per Share (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESScheduleofStockbasedCompensationExpenseforStockOptionsRSAsandRSUsDetails" roleURI="http://www.costar.com/role/SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESScheduleofStockbasedCompensationExpenseforStockOptionsRSAsandRSUsDetails">
        <link:definition>9955528 - Disclosure - SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Schedule of Stock-based Compensation Expense for Stock Options, RSAs, and RSUs (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESScheduleofStockbasedCompensationExpenseforStockOptionsRSAsandRSUsDetails_1" roleURI="http://www.costar.com/role/SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESScheduleofStockbasedCompensationExpenseforStockOptionsRSAsandRSUsDetails_1">
        <link:definition>9955528 - Disclosure - SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Schedule of Stock-based Compensation Expense for Stock Options, RSAs, and RSUs (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESDealContingentForeignCurrencyForwardContractsDetails" roleURI="http://www.costar.com/role/SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESDealContingentForeignCurrencyForwardContractsDetails">
        <link:definition>9955529 - Disclosure - SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Deal-Contingent Foreign Currency Forward Contracts (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESScheduleofCashCashEquivalentsandRestrictedCashDetails" roleURI="http://www.costar.com/role/SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESScheduleofCashCashEquivalentsandRestrictedCashDetails">
        <link:definition>9955530 - Disclosure - SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Schedule of Cash, Cash Equivalents, and Restricted Cash (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESScheduleofAllowanceForCreditLossesForTradeReceivablesDetails" roleURI="http://www.costar.com/role/SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESScheduleofAllowanceForCreditLossesForTradeReceivablesDetails">
        <link:definition>9955531 - Disclosure - SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Schedule of Allowance For Credit Losses For Trade Receivables (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESScheduleofInventoriesRelatedtotheMatterportAcquisitionDetails" roleURI="http://www.costar.com/role/SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESScheduleofInventoriesRelatedtotheMatterportAcquisitionDetails">
        <link:definition>9955532 - Disclosure - SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Schedule of Inventories Related to the Matterport Acquisition (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESScheduleofConstructionInProgressDetails" roleURI="http://www.costar.com/role/SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESScheduleofConstructionInProgressDetails">
        <link:definition>9955533 - Disclosure - SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Schedule of Construction In Progress (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESLeasingOperationsandOtherIncomeExpenseNetDetails" roleURI="http://www.costar.com/role/SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESLeasingOperationsandOtherIncomeExpenseNetDetails">
        <link:definition>9955534 - Disclosure - SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Leasing Operations and Other Income (Expense), Net (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESScheduleofDeferredLeaseIncomeDetails" roleURI="http://www.costar.com/role/SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESScheduleofDeferredLeaseIncomeDetails">
        <link:definition>9955535 - Disclosure - SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Schedule of Deferred Lease Income (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESScheduleofComponentsofOtherExpenseNetDetails" roleURI="http://www.costar.com/role/SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESScheduleofComponentsofOtherExpenseNetDetails">
        <link:definition>9955536 - Disclosure - SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Schedule of Components of Other (Expense), Net (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="REVENUEFROMCONTRACTSWITHCUSTOMERSScheduleofDisaggregatedRevenueDetails" roleURI="http://www.costar.com/role/REVENUEFROMCONTRACTSWITHCUSTOMERSScheduleofDisaggregatedRevenueDetails">
        <link:definition>9955537 - Disclosure - REVENUE FROM CONTRACTS WITH CUSTOMERS - Schedule of Disaggregated Revenue (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="REVENUEFROMCONTRACTSWITHCUSTOMERSNarrativeDetails" roleURI="http://www.costar.com/role/REVENUEFROMCONTRACTSWITHCUSTOMERSNarrativeDetails">
        <link:definition>9955538 - Disclosure - REVENUE FROM CONTRACTS WITH CUSTOMERS - Narrative (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="REVENUEFROMCONTRACTSWITHCUSTOMERSNarrativeDetails_1" roleURI="http://www.costar.com/role/REVENUEFROMCONTRACTSWITHCUSTOMERSNarrativeDetails_1">
        <link:definition>9955538 - Disclosure - REVENUE FROM CONTRACTS WITH CUSTOMERS - Narrative (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="REVENUEFROMCONTRACTSWITHCUSTOMERSScheduleofDeferredRevenueDetails" roleURI="http://www.costar.com/role/REVENUEFROMCONTRACTSWITHCUSTOMERSScheduleofDeferredRevenueDetails">
        <link:definition>9955539 - Disclosure - REVENUE FROM CONTRACTS WITH CUSTOMERS - Schedule of Deferred Revenue (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="REVENUEFROMCONTRACTSWITHCUSTOMERSScheduleofChangesinDeferredRevenueDetails" roleURI="http://www.costar.com/role/REVENUEFROMCONTRACTSWITHCUSTOMERSScheduleofChangesinDeferredRevenueDetails">
        <link:definition>9955540 - Disclosure - REVENUE FROM CONTRACTS WITH CUSTOMERS - Schedule of Changes in Deferred Revenue (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="REVENUEFROMCONTRACTSWITHCUSTOMERSScheduleofContractAssetsDetails" roleURI="http://www.costar.com/role/REVENUEFROMCONTRACTSWITHCUSTOMERSScheduleofContractAssetsDetails">
        <link:definition>9955541 - Disclosure - REVENUE FROM CONTRACTS WITH CUSTOMERS - Schedule of Contract Assets (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="REVENUEFROMCONTRACTSWITHCUSTOMERSScheduleofCommissionsExpenseDetails" roleURI="http://www.costar.com/role/REVENUEFROMCONTRACTSWITHCUSTOMERSScheduleofCommissionsExpenseDetails">
        <link:definition>9955542 - Disclosure - REVENUE FROM CONTRACTS WITH CUSTOMERS - Schedule of Commissions Expense (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="ACQUISITIONSNarrativeDetails" roleURI="http://www.costar.com/role/ACQUISITIONSNarrativeDetails">
        <link:definition>9955543 - Disclosure - ACQUISITIONS - Narrative (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="ACQUISITIONSScheduleofPurchaseConsiderationDetails" roleURI="http://www.costar.com/role/ACQUISITIONSScheduleofPurchaseConsiderationDetails">
        <link:definition>9955544 - Disclosure - ACQUISITIONS - Schedule of Purchase Consideration (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="ACQUISITIONSScheduleofAcquiredAssetsandAssumedLiabilitiesDetails" roleURI="http://www.costar.com/role/ACQUISITIONSScheduleofAcquiredAssetsandAssumedLiabilitiesDetails">
        <link:definition>9955545 - Disclosure - ACQUISITIONS - Schedule of Acquired Assets and Assumed Liabilities (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="ACQUISITIONSScheduleofEstimatedUsefulLivesDetails" roleURI="http://www.costar.com/role/ACQUISITIONSScheduleofEstimatedUsefulLivesDetails">
        <link:definition>9955546 - Disclosure - ACQUISITIONS - Schedule of Estimated Useful Lives (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="ACQUISITIONSScheduleofPurchaseConsiderationMatterportAcquisitionDetails" roleURI="http://www.costar.com/role/ACQUISITIONSScheduleofPurchaseConsiderationMatterportAcquisitionDetails">
        <link:definition>9955547 - Disclosure - ACQUISITIONS - Schedule of Purchase Consideration Matterport Acquisition (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="ACQUISITIONSScheduleofUnauditedProFormaFinancialInformationDetails" roleURI="http://www.costar.com/role/ACQUISITIONSScheduleofUnauditedProFormaFinancialInformationDetails">
        <link:definition>9955548 - Disclosure - ACQUISITIONS - Schedule of Unaudited Pro Forma Financial Information (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="INVESTMENTSANDFAIRVALUEMEASUREMENTSDetails" roleURI="http://www.costar.com/role/INVESTMENTSANDFAIRVALUEMEASUREMENTSDetails">
        <link:definition>9955549 - Disclosure - INVESTMENTS AND FAIR VALUE MEASUREMENTS (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="LEASESNarrativeDetails" roleURI="http://www.costar.com/role/LEASESNarrativeDetails">
        <link:definition>9955550 - Disclosure - LEASES - Narrative (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="LEASESScheduleofComponentsofLeaseExpenseDetails" roleURI="http://www.costar.com/role/LEASESScheduleofComponentsofLeaseExpenseDetails">
        <link:definition>9955551 - Disclosure - LEASES - Schedule of Components of Lease Expense (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="LEASESScheduleofComponentsofLeaseExpenseDetails_1" roleURI="http://www.costar.com/role/LEASESScheduleofComponentsofLeaseExpenseDetails_1">
        <link:definition>9955551 - Disclosure - LEASES - Schedule of Components of Lease Expense (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="LEASESScheduleofSupplementalBalanceSheetInformationRelatedtoLeasesDetails" roleURI="http://www.costar.com/role/LEASESScheduleofSupplementalBalanceSheetInformationRelatedtoLeasesDetails">
        <link:definition>9955552 - Disclosure - LEASES - Schedule of Supplemental Balance Sheet Information Related to Leases (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="LEASESScheduleofSupplementalCashFlowInformationforLeasesDetails" roleURI="http://www.costar.com/role/LEASESScheduleofSupplementalCashFlowInformationforLeasesDetails">
        <link:definition>9955553 - Disclosure - LEASES - Schedule of Supplemental Cash Flow Information for Leases (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="GOODWILLScheduleofGoodwillDetails" roleURI="http://www.costar.com/role/GOODWILLScheduleofGoodwillDetails">
        <link:definition>9955554 - Disclosure - GOODWILL - Schedule of Goodwill (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="GOODWILLNarrativeDetails" roleURI="http://www.costar.com/role/GOODWILLNarrativeDetails">
        <link:definition>9955555 - Disclosure - GOODWILL - Narrative (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="INTANGIBLEASSETSScheduleofIntangibleAssetsDetails" roleURI="http://www.costar.com/role/INTANGIBLEASSETSScheduleofIntangibleAssetsDetails">
        <link:definition>9955556 - Disclosure - INTANGIBLE ASSETS - Schedule of Intangible Assets (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="INTANGIBLEASSETSNarrativeDetails" roleURI="http://www.costar.com/role/INTANGIBLEASSETSNarrativeDetails">
        <link:definition>9955557 - Disclosure - INTANGIBLE ASSETS - Narrative (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="LONGTERMDEBTScheduleofComponentsofOutstandingDebtDetails" roleURI="http://www.costar.com/role/LONGTERMDEBTScheduleofComponentsofOutstandingDebtDetails">
        <link:definition>9955558 - Disclosure - LONG-TERM DEBT - Schedule of Components of Outstanding Debt (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="LONGTERMDEBTNarrativeDetails" roleURI="http://www.costar.com/role/LONGTERMDEBTNarrativeDetails">
        <link:definition>9955559 - Disclosure - LONG-TERM DEBT - Narrative (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="LONGTERMDEBTNarrativeDetails_1" roleURI="http://www.costar.com/role/LONGTERMDEBTNarrativeDetails_1">
        <link:definition>9955559 - Disclosure - LONG-TERM DEBT - Narrative (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="LONGTERMDEBTScheduleofInterestExpenseDetails" roleURI="http://www.costar.com/role/LONGTERMDEBTScheduleofInterestExpenseDetails">
        <link:definition>9955560 - Disclosure - LONG-TERM DEBT - Schedule of Interest Expense (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="INCOMETAXESDetails" roleURI="http://www.costar.com/role/INCOMETAXESDetails">
        <link:definition>9955561 - Disclosure - INCOME TAXES (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="COMMITMENTSANDCONTINGENCIESScheduleofSignificantContractualObligationsandMaturitiesofLongtermDebtDetails" roleURI="http://www.costar.com/role/COMMITMENTSANDCONTINGENCIESScheduleofSignificantContractualObligationsandMaturitiesofLongtermDebtDetails">
        <link:definition>9955562 - Disclosure - COMMITMENTS AND CONTINGENCIES - Schedule of Significant Contractual Obligations and Maturities of Long-term Debt (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="COMMITMENTSANDCONTINGENCIESNarrativeDetails" roleURI="http://www.costar.com/role/COMMITMENTSANDCONTINGENCIESNarrativeDetails">
        <link:definition>9955563 - Disclosure - COMMITMENTS AND CONTINGENCIES - Narrative (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="SEGMENTREPORTINGNarrativeDetails" roleURI="http://www.costar.com/role/SEGMENTREPORTINGNarrativeDetails">
        <link:definition>9955564 - Disclosure - SEGMENT REPORTING - Narrative (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="SEGMENTREPORTINGScheduleofEBITDAandAdjustedEBITDAInformationByOperatingSegmentDetails" roleURI="http://www.costar.com/role/SEGMENTREPORTINGScheduleofEBITDAandAdjustedEBITDAInformationByOperatingSegmentDetails">
        <link:definition>9955565 - Disclosure - SEGMENT REPORTING - Schedule of EBITDA and Adjusted EBITDA Information By Operating Segment (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="SEGMENTREPORTINGScheduleofEBITDAandAdjustedEBITDAInformationByOperatingSegmentDetails_1" roleURI="http://www.costar.com/role/SEGMENTREPORTINGScheduleofEBITDAandAdjustedEBITDAInformationByOperatingSegmentDetails_1">
        <link:definition>9955565 - Disclosure - SEGMENT REPORTING - Schedule of EBITDA and Adjusted EBITDA Information By Operating Segment (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="SEGMENTREPORTINGScheduleofReconciliationofNetLossIncometoEBITDADetails" roleURI="http://www.costar.com/role/SEGMENTREPORTINGScheduleofReconciliationofNetLossIncometoEBITDADetails">
        <link:definition>9955566 - Disclosure - SEGMENT REPORTING - Schedule of Reconciliation of Net (Loss) Income to EBITDA (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="STOCKHOLDERSEQUITYDetails" roleURI="http://www.costar.com/role/STOCKHOLDERSEQUITYDetails">
        <link:definition>9955567 - Disclosure - STOCKHOLDERS' EQUITY (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="EMPLOYEEBENEFITPLANSStockIncentivePlansNarrativeDetails" roleURI="http://www.costar.com/role/EMPLOYEEBENEFITPLANSStockIncentivePlansNarrativeDetails">
        <link:definition>9955568 - Disclosure - EMPLOYEE BENEFIT PLANS - Stock Incentive Plans Narrative (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="EMPLOYEEBENEFITPLANSScheduleofOptionActivityDetails" roleURI="http://www.costar.com/role/EMPLOYEEBENEFITPLANSScheduleofOptionActivityDetails">
        <link:definition>9955569 - Disclosure - EMPLOYEE BENEFIT PLANS - Schedule of Option Activity (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="EMPLOYEEBENEFITPLANSScheduleofFairValueAssumptionforOptionsGrantedDetails" roleURI="http://www.costar.com/role/EMPLOYEEBENEFITPLANSScheduleofFairValueAssumptionforOptionsGrantedDetails">
        <link:definition>9955570 - Disclosure - EMPLOYEE BENEFIT PLANS - Schedule of Fair Value Assumption for Options Granted (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="EMPLOYEEBENEFITPLANSRSAsandRSUsDetails" roleURI="http://www.costar.com/role/EMPLOYEEBENEFITPLANSRSAsandRSUsDetails">
        <link:definition>9955571 - Disclosure - EMPLOYEE BENEFIT PLANS - RSAs and RSUs (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="EMPLOYEEBENEFITPLANSScheduleofRSAsandRSUsActivityDetails" roleURI="http://www.costar.com/role/EMPLOYEEBENEFITPLANSScheduleofRSAsandRSUsActivityDetails">
        <link:definition>9955572 - Disclosure - EMPLOYEE BENEFIT PLANS - Schedule of RSAs and RSUs Activity (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
    </xs:appinfo>
  </xs:annotation>
  <xs:element id="csgp_AccruedLiabilitiesAndOtherLiabilitiesCurrent" abstract="false" name="AccruedLiabilitiesAndOtherLiabilitiesCurrent" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="csgp_OperatingAndFinanceLeaseLiabilityCurrent" abstract="false" name="OperatingAndFinanceLeaseLiabilityCurrent" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="csgp_LeaseAndOtherLiabilitiesNoncurrent" abstract="false" name="LeaseAndOtherLiabilitiesNoncurrent" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="csgp_MatterportMember" abstract="true" name="MatterportMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="csgp_AdjustmentsToAdditionalPaidInCapitalRestrictedStockSurrendered" abstract="false" name="AdjustmentsToAdditionalPaidInCapitalRestrictedStockSurrendered" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="csgp_NonCashLeaseExpense" abstract="false" name="NonCashLeaseExpense" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="csgp_UnrealizedGainLossOnInvestmentsAndDerivatives" abstract="false" name="UnrealizedGainLossOnInvestmentsAndDerivatives" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="csgp_IncreaseDecreaseDeferredCommissions" abstract="false" name="IncreaseDecreaseDeferredCommissions" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="csgp_IncreaseDecreaseInLitigationAccrual" abstract="false" name="IncreaseDecreaseInLitigationAccrual" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="csgp_IncreaseDecreaseInLeaseLiability" abstract="false" name="IncreaseDecreaseInLeaseLiability" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="csgp_PaymentsToAcquirePropertyAndEquipmentAndOtherAssets" abstract="false" name="PaymentsToAcquirePropertyAndEquipmentAndOtherAssets" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="csgp_ProceedsFromExerciseOfStockOptionsAndEspp" abstract="false" name="ProceedsFromExerciseOfStockOptionsAndEspp" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="csgp_CapitalExpendituresIncurredButNotYetPaidAndNoncashLandlordIncentives" abstract="false" name="CapitalExpendituresIncurredButNotYetPaidAndNoncashLandlordIncentives" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="csgp_GoodwillAbstract" abstract="true" name="GoodwillAbstract" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="csgp_AssetAcquisitionPolicyPolicyTextBlock" abstract="false" name="AssetAcquisitionPolicyPolicyTextBlock" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:textBlockItemType"/>
  <xs:element id="csgp_ScheduleOfServiceOrProductTableTextBlock" abstract="false" name="ScheduleOfServiceOrProductTableTextBlock" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:textBlockItemType"/>
  <xs:element id="csgp_ScheduleofCommissionsExpenseTableTextBlock" abstract="false" name="ScheduleofCommissionsExpenseTableTextBlock" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:textBlockItemType"/>
  <xs:element id="csgp_SupplementalBalanceSheetInformationRelatedtoLeasesTableTextBlock" abstract="false" name="SupplementalBalanceSheetInformationRelatedtoLeasesTableTextBlock" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:textBlockItemType"/>
  <xs:element id="csgp_ScheduleofSupplementalCashFlowInformationforLeasesTableTextBlock" abstract="false" name="ScheduleofSupplementalCashFlowInformationforLeasesTableTextBlock" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:textBlockItemType"/>
  <xs:element id="csgp_ScheduleOfInterestExpenseTableTextBlock" abstract="false" name="ScheduleOfInterestExpenseTableTextBlock" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:textBlockItemType"/>
  <xs:element id="csgp_SubscriptionBasedLicensingAgreementMinimumTermYears" abstract="false" name="SubscriptionBasedLicensingAgreementMinimumTermYears" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:durationItemType"/>
  <xs:element id="csgp_NoncontrollingInterestInVariableInterestEntityCarryingValue" abstract="false" name="NoncontrollingInterestInVariableInterestEntityCarryingValue" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="csgp_SubscriptionBasedContractsMember" abstract="true" name="SubscriptionBasedContractsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="csgp_PerformanceBasedRestrictedStockMember" abstract="true" name="PerformanceBasedRestrictedStockMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="csgp_DomainMember" abstract="true" name="DomainMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="csgp_ArlingtonVAMember" abstract="true" name="ArlingtonVAMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="csgp_AssetAcquisitionOwnerOccupancyPercentage" abstract="false" name="AssetAcquisitionOwnerOccupancyPercentage" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="xbrli:pureItemType"/>
  <xs:element id="csgp_PercentageOfPropertyOccupied" abstract="false" name="PercentageOfPropertyOccupied" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="xbrli:pureItemType"/>
  <xs:element id="csgp_ExpensesAbstract" abstract="true" name="ExpensesAbstract" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="csgp_DepreciationAndAmortizationLessorAssetUnderOperatingLease" abstract="false" name="DepreciationAndAmortizationLessorAssetUnderOperatingLease" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="csgp_LessorOperatingLeaseIncomeExpenseNet" abstract="false" name="LessorOperatingLeaseIncomeExpenseNet" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="csgp_CoStarMember" abstract="true" name="CoStarMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="csgp_LoopNetMember" abstract="true" name="LoopNetMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="csgp_CommercialRealEstateSegmentMember" abstract="true" name="CommercialRealEstateSegmentMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="csgp_ResidentialRealEstateSegmentMember" abstract="true" name="ResidentialRealEstateSegmentMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="csgp_ChangeinContractwithCustomerLiabilityRollForward" abstract="true" name="ChangeinContractwithCustomerLiabilityRollForward" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="csgp_ContractwithCustomerLiabilityPriorPeriodAmountsRecognized" abstract="false" name="ContractwithCustomerLiabilityPriorPeriodAmountsRecognized" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="csgp_ContractwithCustomerLiabilityNewDeferralsNetofAmountsRecognizedinCurrentPeriod" abstract="false" name="ContractwithCustomerLiabilityNewDeferralsNetofAmountsRecognizedinCurrentPeriod" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="csgp_CommissionsIncurred" abstract="false" name="CommissionsIncurred" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="csgp_CommissionsCapitalizedintheCurrentPeriod" abstract="false" name="CommissionsCapitalizedintheCurrentPeriod" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="csgp_CapitalizedContractCosts" abstract="false" name="CapitalizedContractCosts" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="csgp_ZondaMember" abstract="true" name="ZondaMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="csgp_S2025Q3DividendsMember" abstract="true" name="S2025Q3DividendsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="csgp_BusinessCombinationExchangeRatioOfCommonStock" abstract="false" name="BusinessCombinationExchangeRatioOfCommonStock" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:pureItemType"/>
  <xs:element id="csgp_BusinessAcquisitionReplacementEquityAwardsFairValue" abstract="false" name="BusinessAcquisitionReplacementEquityAwardsFairValue" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="csgp_BusinessCombinationConsiderationTransferredSettlementOfDebt" abstract="false" name="BusinessCombinationConsiderationTransferredSettlementOfDebt" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="csgp_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedRestrictedCash" abstract="false" name="BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedRestrictedCash" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="csgp_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAvailableForSaleDebtSecurities" abstract="false" name="BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAvailableForSaleDebtSecurities" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="csgp_BusinessCombinationRecognizedLiabilityAssumedAccruedExpenses" abstract="false" name="BusinessCombinationRecognizedLiabilityAssumedAccruedExpenses" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="csgp_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLitigationAccrual" abstract="false" name="BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLitigationAccrual" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="csgp_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOtherAssetsAndLiabilities" abstract="false" name="BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOtherAssetsAndLiabilities" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="csgp_BusinessCombinationConsiderationTransferredFairValueOfNoncontrollingInterests" abstract="false" name="BusinessCombinationConsiderationTransferredFairValueOfNoncontrollingInterests" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="csgp_BusinessCombinationRecognizedAssetAcquiredToLiabilityAssumedExcessLessAndGoodwillLessNoncontrollingInterestInSubsidiaries" abstract="false" name="BusinessCombinationRecognizedAssetAcquiredToLiabilityAssumedExcessLessAndGoodwillLessNoncontrollingInterestInSubsidiaries" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="csgp_OperatingLeaseCostAbstract" abstract="true" name="OperatingLeaseCostAbstract" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="csgp_FinanceLeaseCostAbstract" abstract="true" name="FinanceLeaseCostAbstract" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="csgp_FinanceLeaseExpense" abstract="false" name="FinanceLeaseExpense" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="csgp_CashPaidForAmountsIncludedInMeasurementOfLeaseLiabilitiesAbstract" abstract="true" name="CashPaidForAmountsIncludedInMeasurementOfLeaseLiabilitiesAbstract" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="csgp_RightOfUseAssetsObtainedInExchangeForLeaseObligationsAbstract" abstract="true" name="RightOfUseAssetsObtainedInExchangeForLeaseObligationsAbstract" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="csgp_GoodwillAcquiredDuringPeriodAndMeasurementPeriodAdjustment" abstract="false" name="GoodwillAcquiredDuringPeriodAndMeasurementPeriodAdjustment" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="csgp_A2800SeniorNotesMember" abstract="true" name="A2800SeniorNotesMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="csgp_CreditAgreement2024Member" abstract="true" name="CreditAgreement2024Member" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="csgp_A2020CreditAgreementMember" abstract="true" name="A2020CreditAgreementMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="csgp_RevolvingLoansAndLettersOfCreditMember" abstract="true" name="RevolvingLoansAndLettersOfCreditMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="csgp_AlternateBaseRateMember" abstract="true" name="AlternateBaseRateMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="csgp_DebtInstrumentParValueDiscountedRate" abstract="false" name="DebtInstrumentParValueDiscountedRate" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="csgp_LineOfCreditFacilityCovenantComplianceTotalLeverageRatio" abstract="false" name="LineOfCreditFacilityCovenantComplianceTotalLeverageRatio" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:pureItemType"/>
  <xs:element id="csgp_LesseeOperatingLeaseLiabilityToBePaidDueAfterYearFour" abstract="false" name="LesseeOperatingLeaseLiabilityToBePaidDueAfterYearFour" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="csgp_FinanceLeaseLiabilityToBePaidDueAfterYearFour" abstract="false" name="FinanceLeaseLiabilityToBePaidDueAfterYearFour" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="csgp_LongTermDebtMaturityAfterYearFour" abstract="false" name="LongTermDebtMaturityAfterYearFour" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="csgp_LongTermDebtMaturityInterestPaymentsAbstract" abstract="true" name="LongTermDebtMaturityInterestPaymentsAbstract" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="csgp_LongTermDebtMaturityInterestPaymentsRemainderOfFiscalYear" abstract="false" name="LongTermDebtMaturityInterestPaymentsRemainderOfFiscalYear" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="csgp_LongTermDebtMaturityInterestPaymentsYearOne" abstract="false" name="LongTermDebtMaturityInterestPaymentsYearOne" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="csgp_LongTermDebtMaturityInterestPaymentsYearTwo" abstract="false" name="LongTermDebtMaturityInterestPaymentsYearTwo" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="csgp_LongTermDebtMaturityInterestPaymentsYearThree" abstract="false" name="LongTermDebtMaturityInterestPaymentsYearThree" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="csgp_LongTermDebtMaturityInterestPaymentsYearFour" abstract="false" name="LongTermDebtMaturityInterestPaymentsYearFour" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="csgp_LongTermDebtMaturityInterestPaymentsAfterYearFour" abstract="false" name="LongTermDebtMaturityInterestPaymentsAfterYearFour" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="csgp_LongTermDebtMaturityInterestPayments" abstract="false" name="LongTermDebtMaturityInterestPayments" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="csgp_BrownJudgmentMember" abstract="true" name="BrownJudgmentMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="csgp_GeneralAndAdministrativeExpenseExcludePersonnelCosts" abstract="false" name="GeneralAndAdministrativeExpenseExcludePersonnelCosts" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="csgp_NetIncomeLossBeforeInterestAndOtherIncomeExpenseIncomeTaxesDepreciationAndAmortizationEBITDA" abstract="false" name="NetIncomeLossBeforeInterestAndOtherIncomeExpenseIncomeTaxesDepreciationAndAmortizationEBITDA" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="csgp_AdjustedEarningsBeforeInterestTaxDepreciationAndAmortization" abstract="false" name="AdjustedEarningsBeforeInterestTaxDepreciationAndAmortization" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="csgp_AmortizationOfIntangibleAssetsCostofRevenue" abstract="false" name="AmortizationOfIntangibleAssetsCostofRevenue" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="csgp_AmortizationOfIntangibleAssetsNetOfAdjustments" abstract="false" name="AmortizationOfIntangibleAssetsNetOfAdjustments" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="csgp_AcceleratedShareRepurchaseAgreementMember" abstract="true" name="AcceleratedShareRepurchaseAgreementMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="csgp_CoStarGroupInc.2016StockIncentivePlanMember" abstract="true" name="CoStarGroupInc.2016StockIncentivePlanMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="csgp_PerformanceBasedRSAsWithMarketAndPerformanceConditionMember" abstract="true" name="PerformanceBasedRSAsWithMarketAndPerformanceConditionMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="csgp_PerformanceBasedRSUsWithMarketAndPerformanceConditionMember" abstract="true" name="PerformanceBasedRSUsWithMarketAndPerformanceConditionMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="csgp_ShareBasedPaymentArrangementExpenseExpectedAnnualCompensation" abstract="false" name="ShareBasedPaymentArrangementExpenseExpectedAnnualCompensation" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="csgp_PerformanceBasedRSAsWithoutMarketConditionMember" abstract="true" name="PerformanceBasedRSAsWithoutMarketConditionMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="csgp_PerformanceBasedRSUsWithoutMarketConditionMember" abstract="true" name="PerformanceBasedRSUsWithoutMarketConditionMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="csgp_PerformanceBasedRSUsWithMarketConditionMember" abstract="true" name="PerformanceBasedRSUsWithMarketConditionMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
</xs:schema>
