CoStar Accuses Zillow of Ongoing Infringement in Amended Complaint

CoStar Group has escalated its copyright battle with Zillow, filing an amended complaint on the 27th of March that accuses the Seattle-based portal of continuing to use tens of thousands of watermarked CoStar photographs even after being sued, and of republishing images it had previously claimed to remove.

The amended complaint, filed in the Western District of Washington, puts the total number of infringed images at 53,753, up from around 47,000 in the original July 2025 filing. CoStar Group says those images have been displayed across Zillow's platform more than 250,000 times, and that the portal has been syndicating them to partner sites, including Redfin and Realtor.com, under deals that make Zillow the exclusive provider of multifamily listings to both.

CoStar claims Zillow added 6,774 new infringing images to its platforms after the original complaint was lodged, despite receiving four separate letters between August 2025 and February 2026 identifying the new infringements. It also alleges Zillow re-published images from the original complaint that it had previously purported to take down, some as recently as February 2026.

The filing goes further in detailing how Zillow allegedly uses the images beyond simply displaying them. CoStar contends Zillow feeds the photographs into its Zestimate valuation model and uses them to train recommendation algorithms, and that the portal builds "unclaimed" property pages populated with CoStar images to lure property managers into becoming paying customers.

One of the sharper accusations in the amended filing is that Zillow's own image recognition software, capable of detecting features such as granite countertops from pixel-level analysis, could readily identify CoStar's watermark. CoStar says Zillow simply chooses not to use it for that purpose.

An internal Zillow document from December 2024, cited in the complaint, showed the company was aware of the risk of a CoStar lawsuit before it happened. CoStar's general counsel Gene Boxer said:

"Since CoStar Group filed this lawsuit in July 2025, Zillow's infringement has only gotten worse, and increasingly brazen. Zillow infringed thousands of new CoStar copyrighted images after being sued, many plainly stamped with our watermark, bringing the total number of images at issue to more than 53,000.

Even worse, after claiming to have removed the images CoStar specifically identified in its original complaint, Zillow turned around and re-published many of those very same photographs. Zillow has the tools to stop, it is simply choosing not to, hoping that its mass-infringement scheme will return a profit. We look forward to holding Zillow to account."

CoStar is seeking a permanent injunction, substantial damages, and a court-ordered purge of all its images from Zillow's systems. Zillow has not yet responded publicly to the amended filing.