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UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 10-K

For the fiscal year ended December 31, 2025

OR

For the transition period from ______ to ______

Commission file number 0-24531

CoStar Group, Inc.

(Exact name of registrant as specified in its charter)

(Address of principal executive offices) (zip code)

(202) 346-6500

(Registrant’s telephone number, including area code)

Securities registered pursuant to Section 12(b) of the Act:

Securities registered pursuant to section 12(g) of the Act: None

Indicate by check mark if the registrant is a well-known seasoned issuer, as defined in Rule 405 of the Securities Act. Yes x No o

Indicate by check mark if the registrant is not required to file reports pursuant to Section 13 or Section 15(d) of the Act. Yes o No x

Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports) and (2) has been subject to such filing requirements for the past 90 days. Yes x No o

Indicate by check mark whether the registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S-T (§232.405 of this chapter) during the preceding 12 months (or for such shorter period that the registrant was required to submit such files). Yes x No o

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company, or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company,” and "emerging growth company" in Rule 12b-2 of the Exchange Act.

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. o

Indicate by check mark whether the registrant has filed a report on and attestation to its management’s assessment of the effectiveness of its internal control over financial reporting under Section 404(b) of the Sarbanes-Oxley Act (15 U.S.C. 7262(b)) by the registered public accounting firm that prepared or issued its audit report. x

If securities are registered pursuant to Section 12(b) of the Act, indicate by check mark whether the financial statements of the registrant included in the filing reflect the correction of an error to previously issued financial statements. o

Indicate by checkmark whether any of those error corrections are restatements that required a recovery analysis of incentive-based compensation received by any of the registrant's executive officers during the relevant recovery period pursuant to §240.10D-1(b). o

Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Act). Yes ☐ No x

As of June 30, 2025, the aggregate market value of the common stock (based upon the closing price of the stock on the Nasdaq Global Select Market) of the registrant held by non-affiliates was approximately $33.9 billion. As of February 20, 2026, 419,793,301 shares of common stock were outstanding.

DOCUMENTS INCORPORATED BY REFERENCE

Portions of the registrant’s definitive proxy statement, which is expected to be filed with the Securities and Exchange Commission within 120 days after the end of the registrant’s fiscal year ended December 31, 2025 are incorporated by reference into Part III of this Report.

TABLE OF CONTENTS

Glossary of Terms

The following abbreviations or acronyms used in this Annual Report on Form 10-K (this "Report") are defined below:

Cautionary Statement Concerning Forward-Looking Statements

We have made forward-looking statements in this Report and make forward-looking statements in our other reports filed with the SEC, press releases, and conference calls that are subject to risks and uncertainties. Forward-looking statements include information that is not purely historic fact. Sections of this Report that contain forward-looking statements include “Business,” “Risk Factors,” “Properties,” “Legal Proceedings,” “Management’s Discussion and Analysis of Financial Condition and Results of Operations,” “Quantitative and Qualitative Disclosures About Market Risk,” “Controls and Procedures,” and the Consolidated Financial Statements and related Notes.

Our forward-looking statements are also identified by words such as “hope,” “anticipate,” “may,” “likely,” “might,” “believe,” “expect,” “observe,” “consider,” “think,” “intend,” “envision,” “will,” “should,” “could,” “would,” “plan,” “target,” “estimate,” “predict,” “continue,” “commit,” and “potential” or the negative of these terms or other comparable terminology. You should understand that these forward-looking statements are estimates reflecting our judgment, beliefs, and expectations, not guarantees of future performance. They are subject to a number of assumptions, risks, and uncertainties that could cause actual results to differ materially from those expressed or implied in the forward-looking statements. The following important factors, in addition to those discussed or referred to under the heading “Risk Factors,” and other unforeseen events or circumstances, could affect our future results and could cause those results or other outcomes to differ materially from those expressed or implied in our forward-looking statements:

• the risks related to AI Technologies, such as Homes AI;

• our inability to attract and retain new clients;

• our inability to successfully develop and introduce new or updated online marketplace services, information, and analytics;

• our inability to compete successfully against existing or future competitors in attracting advertisers and in general;

• the effects of fluctuations and market cyclicality;

• the effects of global economic uncertainties and downturns or a downturn or consolidation in the real estate industry;

• our inability to hire qualified persons for, or retain and continue to develop, our sales force, or unproductivity of our sales force;

• our inability to retain and attract highly capable management and operating personnel;

• the downward pressure that our internal and external investments may place on our operating margins;

• our inability to increase brand awareness;

• our inability to maintain or increase internet traffic to our marketplaces, and the risk that the methods, including Google Analytics, that we use to measure average monthly unique visitors to our portals may misstate the actual number of unique persons who visit our network of mobile applications and websites for a given month or may differ from the methods used by competitors;

• our inability to attract new advertisers;

• our inability to successfully identify, finance, integrate, and/or manage costs related to acquisitions;

• our inability to complete certain strategic transactions if a proposed transaction is subject to review or approval by regulatory authorities pursuant to applicable laws or regulations;

• our inability to realize the benefits of the Matterport Acquisition or the Domain Acquisition;

• the inability of third-party suppliers upon which Matterport relies to fulfill its needs;

• the effects of cyberattacks and security vulnerabilities, and technical problems or disruptions;

• the significant costs associated with undertaking a large infrastructure project;

• our inability to generate increased revenue from our current or future geographic expansion plans;

• the risks related to acceptance of credit cards and debit cards and facilitation of other customer payments;

• the effects of climate-related events and other events beyond our control;

• the effects related to attention to climate-related risk and opportunities;

• our inability to obtain and maintain accurate, comprehensive, or reliable data;

• our inability to obtain and maintain stable data feeds, or disruption of our data feeds;

• our inability to enforce or defend our ownership and use of intellectual property;

• the effects of use of new and evolving technologies, including AI, on our ability to protect our data and intellectual property from misappropriation by third parties;

• our inability to defend against potential legal liability for collecting, displaying, or distributing information;

• our inability to obtain or retain listings from real estate brokers, agents, property owners, and apartment property managers;

• our inability to maintain or establish relationships with third-party listing providers;

• our inability to comply with the rules and compliance requirements of MLSs;

• the risks related to open source software;

• the risks related to international operations;

• the effects of foreign currency exchange rate fluctuations;

• our indebtedness;

• the effects of a lowering or withdrawal of the ratings assigned to our debt securities by rating agencies;

• the effects of any actual or perceived failure to comply with privacy or data protection laws, regulations, or standards;

• the effects of changes in tax laws, regulations, or fiscal and tax policies;

• the effects of third-party claims, litigation, regulatory proceedings, or government investigations; and

• the risks related to return on investment; and

• the risks related to the specific timing, price, and size of repurchases under the Stock Repurchase Program, including that the Stock Repurchase Program may be suspended or discontinued at any time at the Company’s discretion.

Accordingly, you should not place undue reliance on forward-looking statements, which speak only as of, and are based on information available to us on, the date of this Report. All subsequent written and oral forward-looking statements attributable to us or any person acting on our behalf are expressly qualified in their entirety by the cautionary statements contained or referred to in this section. We do not undertake any obligation to update any such statements or release publicly any revisions to these forward-looking statements to reflect new information or events or circumstances after the date of this Report or to reflect the occurrence of unanticipated events, except as required by applicable law. Additionally, certain information disclosed herein or elsewhere (such as our website) is informed by various stakeholder expectations and third-party frameworks. Such information is not necessarily material for purposes of our SEC reporting, even if we use “material” or similar language. Particularly, with respect to climate-related risks and opportunities materiality is subject to various definitions that differ from, and are often more expansive than, the definition under U.S. federal securities laws.

PART I