CoStar Antitrust 

Serving Clients Nationwide

CoStar Group, Inc. operates LoopNet and CoStar, the dominant online platforms for listing and researching commercial properties such as office buildings, warehouses, and retail spaces. Cuneo Gilbert Flannery & LaDuca, LLP (CGFL) is pursuing antitrust claims against CoStar on behalf of the commercial real estate professionals who have been locked into a monopoly with nowhere else to turn. Our firm is committed to restoring competition in markets that affect thousands of brokers, property owners, and the clients they serve.

Case Study: One Real Estate LLC v. CoStar Group, Inc., No. 1:26-cv-01735 (D.D.C.)

CGFL attorneys Michael Flanneryand Evelyn Rileyrepresent One Real Estate LLC, doing business as The ONE Street Company, in a proposed class action against CoStar Group, Inc. and CoStar Realty Information, Inc. The case was filed in the United States District Court for the District of Columbia in May 2026.

CoStar is the dominant provider of online commercial real estate listings and data services in the United States, controlling roughly 90% of both the CRE listings market and the CRE information services market. Its platforms, LoopNet and CoStar, are widely regarded as essential tools for commercial real estate professionals, who have no meaningful alternative. Industry participants have long described paying CoStar's fees as an unavoidable "CoStar Tax."

The case alleges that CoStar did not achieve this dominance through superior products or service. Instead, CoStar has systematically eliminated competition through a three-part anticompetitive scheme: locking customers into de facto exclusive agreements that prevent them from sharing their own listing data with competing platforms; claiming ownership over broker-supplied photographs and deliberately seeding listings with false data so it can threaten copyright litigation against brokers who list elsewhere; and blocking competitors' IP addresses from accessing public-facing broker websites, even when the brokers themselves have given permission for that access.

The One Real Estate case seeks to recover on behalf of direct purchasers, the commercial real estate brokerages that have paid artificially inflated prices as a result of CoStar's conduct. The proposed class includes all persons and entities that directly purchased CRE listing or information services from CoStar from April 14, 2022 through the present.

Have questions? Get in touch with our team today by calling (202) 789-3960 or fill out our online contact form.