US Court Rules Google Illegally Monopolized Ad Tech

What Changed

On April 17, 2025, a US federal court in Virginia ruled that Google had broken antitrust law by monopolizing open-web digital advertising markets.¹ The Justice Department and several states had sued in January 2023, alleging that Google used acquisitions and auction manipulation to undermine competition in the tools publishers use to sell ads. Judge Leonie Brinkema found that Google held illegal monopolies in two markets for open-web display ads: publisher ad servers and ad exchanges.²

Europe Reached the Same Conclusion

In September 2025 the European Commission fined Google €2.95 billion for favouring its own ad exchange, AdX. It found that Google's publisher ad server told AdX in advance the best rival bid it had to beat, and that its buying tools, Google Ads and DV360, mainly placed bids on AdX.³ The Commission's preliminary view was that only selling part of the business would end Google's conflicts of interest. Google instead proposed behavioural changes, which the Commission was still assessing a year later.⁴

No Breakup in the US

On September 2, 2026, Brinkema rejected the Justice Department's request that Google sell AdX and possibly its DFP ad server.⁵ Her opinion, unsealed later that month, orders behavioural remedies instead. Google must:

• connect AdX and DFP to Prebid, the open-source auction tool many publishers use, and let AdX bid into rival ad servers on equal terms;
• give publishers data on winning and losing AdX bids;
• run AdX and DFP without favouring its own tools;
• stop Google Ads bidding directly into DFP or favouring Google's tools because Google owns them.

A monitor will oversee the remedies for six years, and the judge said all of them would be in effect within 15 months.² Google has said it intends to appeal the 2025 liability ruling.⁶

Why It Mattered

The case is about how ads are bought and sold rather than how people are tracked, but it covers the same supply chain. The remedies target auction mechanics, such as one exchange seeing rivals' bids first, that decide how much of an advertiser's budget reaches publishers and how much goes in fees.

Whether they change much is open. Digiday notes that the clearest test will be whether publishers start using rival ad tech and Google's share falls.⁶ The ruling also confirmed a pattern on this timeline: as with the UK regulator's oversight of Chrome's cookie plans, competition authorities, not privacy regulators, are deciding how much control Google keeps over the ad market.