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In a legal showdown that could shake the foundations of the online real estate market, Compass filed a lawsuit Monday against Zillow, accusing the home search titan of abusing its market dominance by banning private listings and coercing competition into submission.

Filed in the Southern District of New York, the suit alleges that Zillow’s updated policy — which will begin penalizing non-compliant listings by June 30 — aims to corner the market by punishing sellers who don’t immediately post their homes on Zillow. Compass claims this isn’t a policy shift — it’s an antitrust grenade.

Private Listings: The Battle Over “Fresh Bread” vs. “Stale Crumbs”

According to the lawsuit, Zillow’s new rules block any property from appearing on its platform if it hasn’t been shared publicly within a day. After three such violations, listings will be barred altogether. Compass contends that this essentially cripples the ability of sellers to test marketing strategies, maintain privacy, or gauge interest in a controlled environment.

Compass likened Zillow’s fear of private listings to a fear of becoming a marketplace of “stale bread” — homes that have lingered too long without serious buyer engagement. Without first-access to the most in-demand homes, Zillow’s platform loses value for agents who buy leads and for users looking for the latest listings.

"No company should have the power to ban agents or listings simply because they don't follow that company’s business model," said Compass CEO Robert Reffkin. “That’s not competition. It’s coercion.”

Allegations of a Real Estate Cartel

But Compass isn’t just pointing fingers at Zillow. The lawsuit also implicates Redfin and ExP Realty as co-conspirators, though they are not named as defendants. Compass claims the trio colluded to enforce the ban, forming a “horizontal agreement” — a per se violation of Section 1 of the Sherman Act — aimed at eliminating alternative listing practices and preserving market power.

According to the suit, Redfin invited Compass to join the scheme but was rebuffed. The alleged goal? Ensure no brokerage gained access to listings the others didn’t have — effectively freezing out innovative or privacy-minded sellers.

The lawsuit also notes that Redfin’s recent revenue-sharing pact with Zillow for multifamily listings, now reportedly under antitrust scrutiny, served as motivation to align policies.

Zillow Fires Back: “Hiding Listings Hurts Everyone”

Zillow responded with a sharp rebuttal, dismissing Compass’ claims as baseless and pledging a vigorous defense.

“When a listing is publicly marketed, it should be accessible to all buyers — across all platforms,” a Zillow spokesperson said. “Hiding listings fragments the market, limits consumer choice, and undermines affordability.”

Zillow claims the policy is backed by consumer advocates, fair housing experts, and most brokerages, asserting it benefits buyers, sellers, and agents alike.

Antitrust and Monopoly Claims Take Center Stage

Compass' complaint is a legal minefield for Zillow, alleging:

• Unlawful restraint of trade

• Illegal monopoly maintenance

• Vertical and horizontal anticompetitive conduct

Compass insists Zillow’s policy has no procompetitive benefits to outweigh its market-damaging effects. With over 60% market share in the home search sector, Compass argues, Zillow’s move is less about improving user experience and more about protecting its control over the listing pipeline and revenue model.

The suit asserts that sellers who don’t comply with Zillow’s demands risk losing access to the largest audience in the housing market, making the policy an unfair chokehold on competition and consumer freedom.

Legal Firepower on Both Sides

Compass is represented by Luke Taeschler, Kenneth Dintzer, Daniel A. Sasse, and Chahira Solh of Crowell & Moring LLP. Zillow’s legal team has not been publicly disclosed, and representatives for Redfin and ExP have not commented.