Google acted illegally to establish and defend monopolies in crucial parts of the online advertising technology sector, a federal judge in Virginia ruled Thursday, dealing another antitrust blow to the search giant’s complex digital advertising business.
In a detailed 115-page memorandum opinion, Judge Leonie M. Brinkema determined that Google unlawfully maintained monopoly control over systems that place ads across the open web, specifically the markets for publisher ad servers and ad exchanges, and illegally tied those services together, harming competition and publishers. This decision, stemming from an antitrust action brought by the U.S. Department of Justice and seventeen states (first filed in January 2023), marks the second time in less than a year a federal court has found Google in violation of antitrust law, following an August 2024 ruling finding a monopoly in online search.
The new ruling specified that Google “willfully acquir[ed] and maintain[ed] monopoly power” in the worldwide markets for open-web display publisher ad servers – where its DoubleClick for Publishers (DFP, now part of Google Ad Manager or GAM) holds a market share consistently between 84% and 91% – and open-web display ad exchanges, led by its AdX platform which handles an estimated 54-65% of total market transactions and is roughly nine times larger than its nearest rival.
The court also found Google “unlawfully tied its publisher ad server (DFP) and ad exchange (AdX)” in violation of Sections 1 and 2 of the Sherman Act. A publisher ad server is software publishers use to manage ad inventory, while an ad exchange is a real-time auction platform. The court did, however, dismiss the government’s claim that Google monopolized advertiser ad networks.
How Google Cemented Control Through Tying and Tactics
Central to the court’s findings was how Google leveraged its power, particularly the unique advertising demand flowing through its AdWords system into its AdX exchange. By implementing technical and policy restrictions that effectively required publishers wanting full access to AdX’s real-time bidding features to also use Google’s DFP publisher ad server, the company created a coercive tie.
Evidence showed publishers felt “locked-in,” needing DFP to access AdX’s valuable demand. One ad tech executive from Kevel testified that “[a]lmost every [publisher] ad server has gone out of business because of this integration… It turns out monopolies are pretty effective.”
This AdX-DFP tie enabled Google to deploy a series of anticompetitive tactics through DFP that further fortified its monopolies. These included “First Look,” giving AdX an unfair early bidding advantage, and “Last Look,” allowing AdX to see competitors’ bids before placing its own.
An expert described Last Look as letting AdX “open the envelope for the winning bid, know what the winning bid [wa]s, and be able . . . to bid after everybody else.” This was compounded by “sell-side dynamic revenue share,” where AdX used Last Look data – a feature described internally by one Google engineer as “just yet another way for AdX to exploit the last look advantage,” – to strategically adjust its fees, undercutting rivals.
When Google removed Last Look, it introduced “Unified Pricing Rules,” stripping publishers of their ability to set higher minimum prices (floors) for AdX versus other exchanges, further limiting competition.
Court Rejects Google’s Defenses and Market Arguments
Google argued its actions were legitimate product design choices and protected under the “refusal to deal” doctrine. Judge Brinkema rejected these arguments, finding Google’s procompetitive justifications often pretextual or insufficient to outweigh the anticompetitive harm.
The court noted internal documents showed the primary purpose of the AdX-DFP tie and subsequent policies was often to disadvantage rivals. While Google’s lawyers framed the company’s actions as “a story of innovation in response to competition,” the court found the Trinko refusal-to-deal defense inapplicable, stating that Google’s actions involved anticompetitive conditioning imposed on customers through tying, not merely refusing to deal with rivals.
Judge Brinkema wrote, quoting Microsoft, that “[j]udicial deference to product innovation . . . does not mean that a monopolist’s product design decisions are per se lawful,” and that “product redesign is anticompetitive when it coerces consumers and impedes competition,” which Google’s actions did here.
The court also detailed its rationale for defining the distinct worldwide product markets for publisher ad servers and ad exchanges, rejecting Google’s push for a single, broad ad tech market definition. Evidence of AdX maintaining a durable 20% transaction fee (take rate) for over a decade, despite competitor price drops and internal acknowledgements it might be too high, served as direct proof of monopoly power.
Wider Regulatory Climate and Next Steps
This Ad Tech ruling intensifies the legal jeopardy surrounding Google and its $31 billion (in 2023) ad tech business. It follows the August 2024 ruling finding Google illegally monopolized online search. In that separate case, the DOJ is seeking remedies including the potential divestiture of the Chrome browser, with remedy hearings starting April 21, 2025.
For the Ad Tech violations, Judge Brinkema stated the court “will set a briefing schedule and hearing date to determine the appropriate remedies.” The DOJ has previously indicated it seeks structural relief, potentially including the forced sale of parts of Google’s ad tech stack acquired via the 2008 DoubleClick purchase.
The decision adds to mounting regulatory pressure globally. Google faces ongoing scrutiny and lawsuits in Europe over ad tech, including calls from former EU leaders to break up the business.
China also launched an antitrust investigation into Google in February 2025. Additionally, Google lost a significant US antitrust case brought by Epic Games regarding its Android Play Store policies. During the Ad Tech trial, evidence also emerged of Google’s systemic deletion of internal chat messages and misuse of attorney-client privilege. While Judge Brinkema declined to issue sanctions for this spoliation at this time, she noted the decision “should not be understood as condoning Google’s failure to preserve chat evidence.”
