Zillow Sues Compass and Chicago MLS for Alleged Collusion

Zillow has filed a lawsuit against the brokerage Compass and the MLS, Midwest Real Estate Data (MRED), for alleged collusion to hide home listings from buyers.

MRED is a multiple listing service serving the greater Chicago area and parts of three neighbouring states. The MLS has over 43,000 members and has processed more than 264,000 listings with a combined value of $43 billion.

Compass is the largest broker in the country by transaction value, and recently closed the acquisition of Anywhere Real Estate, the second-largest brokerage in the United States.

Zillow's complaint argues that Compass and MRED violate the Sherman Antitrust Act, which prohibits competitors from colluding to harm competition and consumers.

According to Zillow:

[Compass and MRED] conspired to threaten to cut off Zillow’s and any other competitors’ access to all listings — a critical input for competition in the industry — in a naked effort to coerce their competitors to abandon pro-transparency policies.

In April 2026, MRED and Compass announced a formal partnership to expand MRED’s private listing network nationwide. It allowed Compass agents anywhere in the country to enter listings into MRED’s system—supposedly to “protect” those listings from pro-transparency platforms like Zillow. The explicit purpose was to extend MRED’s monopoly leverage far beyond the Chicago region and force competitors nationwide to abandon consumer protections. 

Compass agreed to subsidize the cost of MRED membership for up to 100,000 Compass agents nationwide—a move that could triple MRED’s size and dramatically expand its power to impose its rules on the rest of the industry. In exchange, MRED agreed to use its monopoly over Chicagoland listing data as a weapon against any platform that dared adopt pro-transparency standards.

MRED and Compass ramped up their conspiracy after Zillow announced Zillow Preview, which lets sellers and their agents display pre-market listings publicly. Before those listings hit the MLS, Zillow Preview competes directly with the private listing networks operated by MRED and Compass, offering sellers broad exposure rather than a limited buyer pool. Starting this summer, Zillow Preview listings will also appear on Realtor.com. For MRED, whose monopoly over Chicagoland listing data depends on brokers having no viable alternative, Zillow Preview represented an existential competitive threat— not just a policy disagreement.

In a lengthy post on its website, Zillow labels the alleged collusion as an "illegal conspiracy", pointing to MRED's partnership with Compass to roll out its private listing network nationwide and extend its market leadership in Chicagoland to other markets, thereby disempowering Zillow.

This nationwide rollout would create a major MLS with an exclusivity agreement with Compass, effectively hiding vast swathes of housing stock from any consumer not using a Compass broker to search for a home.

Meanwhile, Zillow says that Compass's acquisition of Anywhere Real Estate gives it a significant market share in several markets—up to 35% in Chicago—which, in Zillow's words, gives Compass "leverage to influence a rulemaking body for its own gain."

Compass recently agreed to withdraw a lawsuit targeting Zillow's listings ban in March, after Zillow announced it would drop its controversial listings ban announced last year. Now it's Zillow's turn to point the finger.