CoStar Group is fighting on multiple legal fronts in 2026. Three antitrust class action lawsuits filed in April accuse the commercial real estate data giant of illegally monopolizing the market for online commercial real estate listings, while CoStar itself is pressing a large copyright infringement case against Zillow and finishing off a related fight with the smaller platform CREXi. Taken together, the CoStar lawsuits are among the most consequential real estate industry cases now pending in federal court.
The 2026 Antitrust Class Actions
On April 15, 2026, Brooklyn brokerage Grand & Co. filed the first antitrust class action against CoStar in the U.S. District Court for the Eastern District of Virginia. The case, Shapiro Hospitalities LLC d/b/a Grand & Co. v. CoStar Group, Inc., et al. (Case No. 1:26-cv-01027), was brought by DiCello Levitt on behalf of commercial real estate brokers and other market participants who allegedly paid inflated fees for CoStar’s products.1DiCello Levitt. DiCello Levitt Files First Antitrust Class Action Against CoStar Group Over Commercial Real Estate Data Monopoly A second class action, Malm, Inc. v. CoStar Group, Inc., et al. (Case No. 2:26-cv-04052), was filed the same day in the Central District of California by Susman Godfrey, Berger Montague, Edelson PC, and Latham & Watkins.2Law360. Malm, Inc. v. CoStar Group, Inc., et al A third followed in Washington, D.C.3Virginia Business. CoStar Faces Multiple Antitrust Lawsuits
The complaints allege violations of Sections 1 and 2 of the Sherman Act. They define the relevant market as internet-based commercial real estate listing and information services, and allege CoStar controls roughly 80% of that market through its CoStar and LoopNet platforms.1DiCello Levitt. DiCello Levitt Files First Antitrust Class Action Against CoStar Group Over Commercial Real Estate Data Monopoly
According to the Grand & Co. complaint, CoStar keeps that share through several specific practices. Its data agreements allegedly impose non-negotiable terms preventing customers from sharing their own listings with competing platforms. It has allegedly coerced the three largest U.S. commercial brokerages — CBRE, JLL, and Cushman & Wakefield — into long-term deals the complaint calls “naked agreements not to compete” in the digital listing market. Clients allegedly must buy subscriptions for every broker at their firm regardless of individual usage, at $300 to $1,000 per broker per month. And CoStar allegedly enforces those restrictions with digital watermarks, IP blocks, and scraping of competitor sites. The plaintiffs say these tactics raised barriers to entry, foreclosed competition, and forced customers to pay artificially inflated prices.4Bisnow. Class Action Accuses CoStar of Anticompetitive Scheme That Destroyed Competition
All three cases seek class certification, jury trials, treble damages, and permanent injunctive relief.5National Law Journal. Commercial Real Estate Data Giant CoStar Faces New Monopolization Claims
CoStar’s Response
CoStar General Counsel Gene Boxer has called the complaints “baseless,” describing them as “scattershot” filings filled with “factual errors, misleading characterizations, and fundamental misunderstandings” of the company’s business. CoStar says its contracts contain standard terms preventing customers from using CoStar-provided data to compete against it, and that customers remain free to share their own listings on other platforms. The company points to the presence of competitors such as CREXi as evidence the market is still competitive.3Virginia Business. CoStar Faces Multiple Antitrust Lawsuits4Bisnow. Class Action Accuses CoStar of Anticompetitive Scheme That Destroyed Competition
Where the Cases Stand
The class actions are in their opening stages. CoStar moved to transfer the California case to the Eastern District of Virginia, where the Grand & Co. case sits. On June 12, 2026, the California court stayed Malm until September 18, 2026, and ordered the parties to report on a pending motion before the Judicial Panel on Multidistrict Litigation, which could consolidate the three cases for coordinated pretrial proceedings.6PACER Monitor. Malm, Inc. v. CoStar Group, Inc., et al CoStar also moved to stay the Virginia proceedings while the transfer questions are resolved.7Virginia Lawyers Weekly. CoStar Federal Antitrust Lawsuits in Virginia, California, D.C.
The CREXi Ruling That Set the Table
The antitrust class actions build on a theory the Ninth Circuit greenlit less than a year earlier. CoStar sued Commercial Real Estate Exchange, known as CREXi, in September 2020 alleging theft of tens of thousands of copyrighted photos and listings. CREXi countersued with eight antitrust claims under the Sherman Act and California’s Cartwright Act. A federal district court in California dismissed those counterclaims twice.8Law and Economics Center. Brief of Former Antitrust Officials to US Supreme Court in CoStar v. CREXi
The Ninth Circuit reversed on June 23, 2025. The panel held that CREXi had plausibly alleged CoStar engaged in “de facto” exclusive dealing with brokers even though CoStar’s contracts had no express exclusivity clauses. It was enough, the court said, that brokers “widely understood” the terms to foreclose their ability to work with competitors, and that CoStar built technological barriers preventing brokers from freely moving their listings to rival platforms. Those practices, the court concluded, could amount to anticompetitive conduct under Sections 1 and 2 of the Sherman Act.9U.S. Court of Appeals for the Ninth Circuit. CoStar Group, Inc. v. Commercial Real Estate Exchange, Inc., No. 23-55662
CoStar asked the U.S. Supreme Court to overturn the ruling, arguing the de facto exclusive dealing theory lacked doctrinal support and created a circuit split. The Court denied the petition on March 23, 2026.10Supreme Court of the United States. CoStar Group, Inc. v. Commercial Real Estate Exchange, Inc., No. 25-667 Weeks later, the class action plaintiffs filed their complaints using the same legal theory.
The underlying CREXi copyright case is moving toward trial. In June 2025, the district court denied both sides’ summary judgment motions but found that CREXi had engaged in a deliberate, company-wide practice of copying LoopNet images and cropping out CoStar’s watermarks using offshore teams in India, and rejected CREXi’s Digital Millennium Copyright Act safe harbor defense.11CoStar Group. Federal Court Finds Rival CREXi Copied and Cropped Thousands of CoStar’s Copyrighted Photos
CoStar v. Zillow
In July 2025, CoStar sued Zillow Group for copyright infringement in the U.S. District Court for the Southern District of New York. The original complaint alleged Zillow used nearly 47,000 CoStar-copyrighted images without authorization, displaying them more than 250,000 times across Zillow’s platforms and through syndication with Redfin and Realtor.com.12ALM Media. CoStar Group, Inc. v. Zillow Group, Inc., Complaint
According to the complaint, Zillow used the photos to build “unclaimed” property pages designed to attract landlords and sell advertising, to curate and rearrange images on active listings to maximize leads, and to feed its “Zestimate” valuation tool. CoStar alleged the infringement was willful, noting the visible watermarks and a prior finding of mass copyright infringement of real estate photos against Zillow in a case brought by VHT, Inc., a company CoStar later acquired.12ALM Media. CoStar Group, Inc. v. Zillow Group, Inc., Complaint
An amended complaint filed in March 2026 expanded the claim to more than 53,000 watermarked photos, with CoStar alleging that infringement continued after the suit was filed and that some images Zillow removed were later republished.13HousingWire. CoStar Zillow 53,000 Photos
Zillow moved in November 2025 to transfer the case to Washington state, where it is headquartered, accusing CoStar of forum shopping. CoStar’s General Counsel called the motion a “transparent attempt to delay justice,” but the company eventually dropped its opposition. On December 4, 2025, Judge Edgardo Ramos granted the transfer to the Western District of Washington.14Online Marketplaces. Zillow Throws Jabs at CoStar and Compass as War of Words Continues15Justia. CoStar Group, Inc. v. Zillow Group, Inc., Transfer Order
On CoStar’s Q3 2025 earnings call, CEO Andy Florance said “Zillow is under siege, facing an unprecedented wave of lawsuits” and suggested the market did not fully appreciate “the sheer magnitude of the risk bearing down on Zillow from all sides.”16Inman. CoStar CEO Andy Florance Says in Earnings Call Zillow Is Under Siege
A Long Litigation Track Record
Aggressive litigation is not new for CoStar. By 2018 the company had filed more than 30 copyright infringement and data theft lawsuits, which Florance has described as necessary to combat “systematic theft of CoStar intellectual property.”17The Real Deal. CoStar Has Long History of Copyright Infringement Lawsuits
- CoStar’s first major copyright suit, filed in 1999 against LoopNet over proprietary photographs, settled in 2003. CoStar acquired LoopNet in 2012 for $860 million, a deal the class action plaintiffs now cite as the foundation of CoStar’s market dominance.
- CoStar sued the platform RealMassive in 2015 for displaying copyrighted photographs; the case settled for $1 million.
- CoStar sued Xceligent in 2016, alleging industrial-scale image theft using offshore researchers. After Xceligent filed for bankruptcy in 2017, a federal judge in the Western District of Missouri entered a $500 million judgment in December 2019, which CoStar’s counsel described as the largest copyright infringement judgment for photographs ever awarded. In practice, Xceligent’s insurers were liable for only about $11 million.18Finance & Commerce. Real Estate Data Dispute Yields $500 Million Judgment19CoStar Group. Xceligent Trustee Agrees to $500 Million Judgment to Settle Claims Company Stole Images From CoStar
The Zillow suit is the first time CoStar has turned its copyright playbook on a top-tier residential real estate competitor, reflecting the company’s push into residential markets through its Homes.com platform.17The Real Deal. CoStar Has Long History of Copyright Infringement Lawsuits
Disclosed Litigation Exposure
CoStar’s Q1 2026 SEC filing discloses a $99 million litigation accrual tied to what it calls the “Brown judgment,” with a possible additional $17 million in post-judgment interest. Restricted cash of $101 million includes collateral held for a litigation bond, and the company identifies its litigation exposure as a “meaningful contingent cash outflow.”20Stock Titan. CoStar Group Inc. Quarterly Earnings Report (10-Q) The three antitrust class actions, if certified and successful, seek treble damages on top of that existing exposure.