What happened in the Google ad tech antitrust case?
In April 2025, US District Judge Leonie Brinkema ruled that Google illegally monopolized the publisher ad server and ad exchange markets and unlawfully tied them together. After a remedies trial in September 2025, she ruled on 2 September 2026 that Google need not sell its AdX exchange, but must meet behavioral rules, including Prebid interoperability, overseen by a six-year monitor.
The US Department of Justice and a group of states sued in January 2023. The 17 April 2025 liability ruling found monopolization in publisher ad servers (DFP) and exchanges (AdX), but rejected the claim of a separate advertiser ad network market. The DOJ sought divestiture of AdX and parts of DFP; Google proposed behavioral fixes. See United States v. Google.
Judge Brinkema's 106-page remedies opinion, unsealed on 16 September 2026, orders Google to build integrations connecting AdX and DFP with Prebid, submit AdX bids to rival publisher ad servers on the same terms as DFP, and share bid data with publishers. The parties were due to propose a final judgment by 2 October 2026, and appeals are expected, so details may still change. The EU pursued a parallel case; see antitrust in ad tech.