COSTAR GROUP, INC.

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 14A

Proxy Statement Pursuant to Section 14(a) of

the Securities Exchange Act of 1934

(Amendment No. )

Filed by the Registrant

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OUR

VALUES

Integrity

We uphold the highest ethical standards at all times. We earn our colleagues’, customers’, and stakeholders’ trust by saying and doing the right thing.

Respect for the Individual

We value diversity and cherish uniqueness. We are inclusive always. CoStar is for all people, without exception. We recognize that the thoughts and feelings of others are as important and valuable as our own.

Work-Life Balance

We work hard and take pride in our professional accomplishments. We are committed to creating value for our customers, while still recognizing the need to have a sacrosanct place for our personal lives and families.

Cohesive Innovation

We create products of vital utility, delivering information and tools that are critical to the success of our customers and industry. Our solutions mobilize individuals to enable them to make confident, intelligent decisions.

Embrace and Drive Change

At our core we are about change. We challenge the status quo and constantly seek a better way.

Build Awesome Things

We work passionately to design and buildawe-inspiring, beautiful products that delight and improve the lives of billions of people. We know that design matters.

Keep the Customer at the Center of All We Do

We succeed only when our customers succeed. We treat each of our customers the way we would prefer to be treated when buying a product or service. We invest in and enjoy the strong bonds and long-lasting, authentic friendships built with our customers.

The Best Teams Anywhere

We hire the best. We work and learn alongside exceptionally talented peers who are passionate about building the best possible workplace and taking our business to great heights. We have azero-tolerance policy for jerks.

Continuous Learning

We are curious. We want to learn, grow, and better ourselves. We view mistakes as a necessary part of learning. Through the expertise we develop, we are better partners to our clients, stockholders, communities, and colleagues.

Be Collaborative

We are all part of the bigger team, and we are at our best when we communicate, empathize, and collaborate.

2026 PROXY STATEMENT

MESSAGE FROM OUR FOUNDER AND CHIEF EXECUTIVE OFFICER

2025 was a pivotal year for CoStar Group, as we continued to execute on our proven value creation playbook and strengthen our global leadership in the digital transformation of the $300+ trillion real estate industry. We have a strong foundation and continue to expand and evolve our platforms to drive our next chapter of profitable growth and margin expansion.

Our core businesses are profitable, stable, and growing – underscored by our 59 th consecutive quarter of double-digit revenue growth in the fourth quarter of 2025. In 2025, we achieved record revenue of $3.2 billion, an increase of 19% over 2024. Adjusted EBITDA for 2025 surged 83% to $442 million, reflecting the immense operating leverage inherent in our platform as we transition from a phase of major investment to one of profitable growth.

I am particularly proud of the progress we are seeing with Homes.com. The platform now attracted 35,000 agent subscribers – 76% of whom are on annual contracts – generating over $100 million in annualizedrun-rate revenue. In just two years, Homes.com has become the fastest-growing residential real estate portal network in the U.S., reaching more than 2.1 billion views and 108 million average monthly unique visitors in 2025.

Delivering on Our Proven Value Creation Strategy

Following recommendations from the Capital Allocation Committee and a comprehensive Board review in 2025, we implemented key business, financial, and governance initiatives focused on accelerating profitability for Homes.com, making disciplined investments in our core platforms, delivering incremental capital returns to stockholders, aligning executive compensation with stockholders’ interests, strengthening corporate governance, and enhancing investor transparency. Our strategic plan has been informed by extensive stockholder engagement, which is integral to the success of the Company. Since the start of 2026, I have greatly valued meeting with 500 stockholders around the world. We appreciate your continued support and feedback.

We continue to invest in expanding our commercial product offerings, including the addition of real estate lease benchmarking, a loan origination module, new homes construction information and analytics, hospitality profit/loss benchmarking, and further international expansion. In 2025, we acquired Matterport, the global leader in 3D digital twin technology, and Domain, one of Australia’s most recognized and trusted property platforms.

These investments enable us to enhance and better execute our proven value creation playbook to unlock the tremendous value of our digital ecosystem and build upon our deep history

of developing and expanding industry-leading platforms through disciplined acquisitions and organic investments.

In particular, Homes.com has reached an inflection point. With the bulk of the investment phase complete, Homes.com is generating positive network effects across our ecosystem, contributing to improved performance at Apartments.com and enabling broader technology integration, including advancements in AI.

In February 2026, we launched Homes Ai – the most sophisticated vertical AI application in real estate. We believe this innovation marks a new era for our business that will allow us to transform each of our platforms and meaningfully differentiate CoStar Group from the rest of the industry. We see meaningful opportunities to extend our Homes Ai and broader AI capabilities across our portfolio – including Apartments.com, CoStar, LoopNet, Land.com, and BizBuySell – ushering in what we believe will be a new era of intelligent, conversational real estate discovery.

As we execute against our strategy, we are committed to being disciplined in our capital allocation and mindful of near-term stockholder returns. To that end, we completed the prior $500 million share repurchase authorization on an accelerated timeframe and the Board authorized a new $1.5 billion share repurchase program.

CoStar Group’s operational and financial achievements would not have been possible without the hard work and dedication of our talented global team of over 8,000 employees. During the year, 13% of employees moved into new roles within the Company, and we maintained an average monthly retention rate of 99%. We are grateful for their continued contributions and commitment to CoStar Group.

Our focus remains on increasing long-term stockholder value, and we look forward to continued stockholder engagement as we work to advance our next chapter. Thank you for your ongoing support and investment in CoStar Group.

ANDREW C. FLORANCE Founder, Chief Executive Officer, and Director

2026 PROXY STATEMENT

MESSAGE FROM OUR

BOARD CHAIR

It is an honor to serve as Chair of the Board of Directors of CoStar Group, alongside a deeply engaged and experienced group of directors. Our Board is actively engaged in overseeing management and supporting long-term value creation on your behalf.

Over the past year, our Board focused on three priorities that we heard matter most to our stockholders: aligning executive compensation withpay-for-performance, disciplined capital allocation, and sustained investment in strategic initiatives to drive durable long-term value creation.

Meaningful Stockholder Engagement and Executive Compensation Alignment

Following the annual meeting of stockholders in 2025, Robert Musslewhite, Chair of our Compensation Committee, and/or I, met personally with 100% of the Company’s top 50 stockholders that responded to the Company’s outreach and agreed to discuss our executive compensation program.

Stockholders we met with emphasized the importance of rigorous performance alignment, transparency, and accountability. In response, the Board—led by the Compensation Committee—redesigned our 2026 executive compensation program with more rigorous, predominantly quantitative performance goals, a simplified structure, and clearerpay-for-performance alignment.

The Board will continue to assess the program regularly and engage with stockholders to ensure it remains fit for purpose.

Disciplined Capital Allocation and Strategic Oversight

The Board maintained close oversight of capital allocation throughout 2025, informed by recommendations of the Capital Allocation Committee, as CoStar Group continues to scale its platforms and pursue opportunities to expand its leadership across commercial and residential real estate globally.

After careful evaluation, the Board supports disciplined investment in Homes.com to advance our long-term strategic direction and strengthen our position in the residential marketplace.

Collaborative Board–Management Partnership

Throughout these efforts, the Board has worked in close partnership with ourfounder-led management team—providing oversight, strategic guidance, and support, while respecting management’s role inday-to-day execution. This collaborative relationship is a defining strength of our governance approach and positions the Company well for continued success.

Board Refreshment and Ongoing Governance Evolution

The Board remains focused on ensuring we have the right skills, perspectives, and experience to guide the Company’s strategy. As a result of our ongoing refreshment efforts, half of our directors have joined within the past three years.

The Board remains firmly committed to strong governance, active stockholder engagement, and disciplined oversight of strategy, compensation, and capital allocation.

On behalf of the Board, thank you for your continued trust and investment in CoStar Group. We respectfully ask for your support on the proposals presented at this year’s Annual Meeting.

LOUISE S. SAMS Board Chair, CoStar Group, Inc.

2026 PROXY STATEMENT

NOTICE OF 2026 ANNUAL MEETING OF STOCKHOLDERS

TUESDAY, JUNE 23, 2026 | 10:00 A.M., EASTERN TIME Exclusively online at www.virtualshareholdermeeting.com/CSGP2026

Items of Business

Review your proxy statement and vote in one of three ways:

Internet Visit the website on your proxy card or voting instruction form

By Telephone Call the telephone number on your proxy card or voting instruction form

By Mail Sign, date, and return your proxy card or voting instruction form in the enclosed envelope

Proposals to be Voted on and Board

Voting Recommendations

Record Date

The Board of Directors has fixed Monday, April 27, 2026, as the record date for determining stockholders entitled to receive notice of and to vote at the Annual Meeting (or any adjournment or postponement of it). Only stockholders of record at the close of business on that date are entitled to notice of and to vote at the Annual Meeting.

Participation in Virtual Annual Meeting

We are pleased to invite you to participate in our Annual Meeting, which will be conducted exclusively online at www.virtualshareholdermeeting.com/CSGP2026. Please see “Other Information” beginning on page 92 of this Proxy Statement for additional information.

Voting

Your vote is very important to us. Please act as soon as possible to vote your shares, even if you plan to participate in the Annual Meeting. For specific instructions on how to vote your shares, please see “Other Information” beginning on page 92 of this Proxy Statement.

By Order of the Board of Directors,

Gene Boxer

General Counsel and Corporate Secretary

April 30, 2026

IMPORTANT NOTICE REGARDING THE AVAILABILITY OF PROXY MATERIALS FOR THE STOCKHOLDER MEETING TO BE HELD ON JUNE 23, 2026: The Notice of Meeting and this Proxy Statement, as well as our Annual Report to Stockholders (the “2025 Annual Report”), are available on our corporate website at https://investors.costargroup.com/financials-filings. We are furnishing proxy materials to some of our stockholders through the Internet instead of through the mail. On or about April 30, 2026, we mailed to stockholders as of the record date a Notice of Internet Availability of Proxy Materials (the “Notice”). The Notice tells you how to access this Proxy Statement and our 2025 Annual Report, as well as how to submit your proxy over the Internet. If you received the Notice and would still like to receive a printed copy of our proxy materials, please follow the instructions in the Notice.