Staff Reports
CoStar Group — parent of Homes.com — just stepped into a high‑stakes fight over who gets to show homes in Chicago. On June 10, 2026, CoStar filed an amicus brief opposing Zillow’s bid for a preliminary injunction in Zillow v. Midwest Real Estate Data (MRED) and Compass. The brief accuses Zillow of asking courts to force MLSs to give Zillow full listing access while Zillow hoards its own pre‑market inventory through a program called Zillow Preview.
CoStar says Zillow is playing by two rules
CoStar’s brief argues the case is simple: Zillow wants other platforms to be open, but keeps its own pre‑market listings exclusive. Zillow Preview, CoStar says, was rolled out with deals that locked up pre‑MLS listings from some 60 brokerages and then got syndicated with Realtor.com. Gene Boxer, CoStar’s General Counsel, calls the arrangement “heads I win, tails you lose.” If true, Zillow would get the benefits of a full MLS feed while denying rivals the valuable early inventory that draws house hunters.
Why the court should care about antitrust and consumer harm
CoStar warns that exclusive pre‑market sites funnel buyers into a single portal’s ecosystem. That matters because portals don’t just show listings — they feed lead generation, mortgage referrals, and other services that can steer consumers and extract fees. The amicus brief argues these practices can harm competition and consumers, and that a court shouldn’t give Zillow sweeping access to MLS data while Zillow’s own Preview listings remain walled off. Judge John J. Tharp Jr. will hear the preliminary‑injunction fight in early July, so the court’s view of these arguments could decide who gets to show Chicago listings for now.
A conservative take: level the playing field, not tip it
Let’s be blunt. Conservatives should want fair markets, not clever favoritism. If Zillow is right to demand equal access to other firms’ listings, it should be willing to open its own pre‑market inventory to the same standard. You can’t preach openness and practice gatekeeping at the same time. Whether you cheer or boo Zillow Preview, the court should apply consistent rules that protect competition and consumers — not bless a one‑sided advantage for the biggest portal in the room.
What to watch next
The July preliminary‑injunction hearing will be the next turning point. If the judge grants Zillow immediate access to MRED’s feed while leaving Zillow Preview exclusive, that will shape who wins eyeballs and leads in Chicago. If the court gives weight to CoStar’s amicus brief, it could deny Zillow the one‑sided relief it seeks. Either way, this fight will matter for how pre‑market listings and MLS access work across the country — and for whether big portals can demand access while hoarding the best inventory for themselves.
