CoStar Group, a leading provider of commercial real estate data and marketplaces, has filed a federal lawsuit in New York accusing Zillow of “rampant copyright infringement” for allegedly publishing more than 46,000 of CoStar’s copyrighted photographs on Zillow.com and partner sites Redfin and Realtor.com. According to the complaint, Zillow’s use of the images—many displaying CoStar’s distinctive watermark—occurred over 250,000 times, creating potential exposure for more than a billion dollars in damages and making it one of the largest image infringement cases in history.

CoStar asserts that it has spent billions of dollars building the world’s largest library of real estate photographs, employing thousands of professional and architectural photographers to capture over two million images annually. The company argues that Zillow chose to exploit these copyrighted assets rather than invest in its own photography and intellectual property. CoStar also highlights that Zillow is a repeat offender, having previously paid millions following a jury verdict in an earlier copyright case involving VHT, Inc.

The alleged infringement is further amplified by Zillow’s partnerships with Redfin and Realtor.com, which rely on Zillow as the exclusive provider of multifamily listings, spreading CoStar’s photos across multiple major platforms. CoStar CEO Andy Florance condemned the activity as “outrageous” and warned that the company will also pursue legal action against Redfin and Realtor.com if the images are not removed immediately.

The lawsuit underscores intensifying tensions in the online real estate marketplace as platforms compete for high-quality visual content to drive traffic and listings. CoStar, whose portfolio includes LoopNet, Apartments.com, Homes.com, and Matterport, says it is committed to enforcing its copyrights and holding infringers accountable to protect decades of investment and its expanding network of digital real estate services.