Zillow Group sued Compass Inc. and Midwest Real Estate Data LLC in the U.S. District Court, Northern District of Illinois.
The complaint alleges Compass and the Chicago-area MLS colluded to hide home listings, pressuring Zillow to join their arrangement.
Zillow claims concealment deprives buyers of full property visibility and harms competition in the residential real‑estate market nationwide.
Following the filing, Zillow shares fell 1.62% and Compass shares dropped 3.77% in after‑hours trading on the same day.