Is Zillow A Monopoly? Lawyers Weigh In On Compass’s Suit

Given the heated rhetoric of Compass CEO Robert Reffkin about Zillow in his recent social media posts, Marx Sterbcow, the managing attorney at Sterbcow Law Group, said the lawsuit Compass filed on Monday was not unexpected.

“I thought this was inevitable when Zillow announced its listing standards policy,” Sterbcow said. “There was a lot of chatter in the legal community about this policy as many felt that it raised significant antitrust concerns.” 

In the complaint, Compass claims that Zillow’s new policy “destroys” its ability to use the first two phases of its three-phase marketing plan — private exclusives and coming soon — harming its business, and that Zillow created the policy to “maintain its monopoly in the home search market.”

“If you are a broker or someone in real estate looking to innovate or create a new piece of tech that involves listings, this policy really kind of crushes your whole model,” Sterbcow said. 

Under the listing standards policy, Zillow is banning any listing not input into the MLS within 24 business hours of the property being publicly marketed. While the policy does allow for office or private exclusive listings, if a client would eventually like the listing to appear on Zillow and it does not sell as a private exclusive, the policy states that the listing broker may only share the office exclusive with other agents in their own brokerage via one-to-one communication. 

Although it will be up to the court to decide whether or not Zillow’s actions were designed to maintain its alleged monopoly power, there is no denying that the firm has a large market share. Data from SimilarWeb shows that in May 2025, Zillow recorded 360.6 million total visits, compared to second ranked site, Realtor.com, which recorded 129 million total visits.

Additionally, according to the complaint, Zillow has more than 60% of the market share when it comes to user traffic.

“That is crucial for monopolization claims, as when you are at 50% to 60% market share, you are very much in the zone for monopoly power,” Harrison McAvoy, a partner at antitrust focused law firm Shinder Cantor Lerner, said. “It seems that they are on strong ground there.”

While one may not initially think that Compass and Zillow are direct competitors, which Compass claims in its complaint, Chuck Cain, an attorney and the president of Alliance Solutions, feels there are compelling reasons to see the two as competitors.

“Back before even COVID, brokers and agents were arguing that Zillow was their direct competition and part of it is because of the network Zillow has created and how it sells leads to agents in its network, like a brokerage gives leads to its agents in exchange for either a cut of their commission or some sort of fee. 

Conspiracy and collusion

In addition to the monopoly claims, the lawsuit also claims that Zillow colluded with alleged “co-conspirators” Redfin and eXp Realty, who were not named as defendants in the lawsuit. The complaint cites comments made in a late night phone call between Redfin CEO Glenn Kelman and Reffkin, during which Compass claims Kleman “revealed information suggesting that Redfin and Zillow had conspired.” 

“Mr. Kelman asked Mr. Reffkin whether Mr. Reffkin had spoken to Zillow’s CEO before Zillow’s announcement and implied that Mr. Kelman had spoken to Zillow before the announcement,” the complaint states.

Despite the alleged comments made during this phone call, McAvoy does not feel the collusion claims in the suit are as strong as the monopoly claims. 

“This is more of a monopolization complaint,” McAvoy said. “To have a monopoly power you need to have monopolization conduct, which is essentially excluding a competitor or potential competitor, which is what Compass is alleging Zillow is doing with this policy.” 

This being said, McAvoy is not writing off the allegations of collusion, saying that it will depend on the evidence presented. 

Next steps for the lawsuit

With Zillow’s listing standards policy scheduled to go into effect this coming Monday, legal experts believe there is a strong likelihood that Compass will file a motion for a preliminary injunction asking the court to order Zillow to delay implementing the policy. 

“My guess is that they will file it right before it goes into effect or maybe an hour or 30 minutes after it goes into effect, which would give them standing for the injunction,” Sterbcow said.

Sterbcow feels that Compass would just ask for a temporary injunction or temporary restraining order in that motion.

While a motion for a preliminary injunction seems like a strong possibility, attorneys warn that these injunctions can sometimes be challenging to get approved. 

As for alleged co-conspirator Redfin, whose own listing standards policy doesn’t go into effect until September, Sterbcow said that if the firm enacts the policy as it is currently slated, it wouldn’t be surprising if Compass filed another lawsuit.

“It is a possibility, but if I were in charge of Redfin, I’d probably delay making any sort of snap decision until I got a sense of what is going on with this lawsuit,” Sterbcow said.

In addition to potential actions taken by Compass, Cain feels that it wouldn’t be a surprise to see an amicus curiae brief from either the Department of Justice (DOJ) or fair housing advocacy groups.

“This is front page kind of stuff — the New York Times covered it, and you definitely don’t want to be in the papers for the wrong reasons,” Cain said.