In her 115-page ruling, Judge Leonie Brinkema found Google liable on three key counts: monopolization of the publisher ad server market, monopolization of the ad exchange market, and unlawfully tying its publisher ad server (DFP) to its ad exchange (AdX).12 The judge determined that Google's practices "substantially harmed" publishers and users across the web by forcing customers to use products they might not have otherwise chosen.23 Brinkema explained that Google's fundamental business is advertising, with nearly 80% of its revenue generated from leveraging user data collected through its free services to match advertisers to users.1

The ruling represents a significant victory for the Department of Justice, though it wasn't a complete win. The court rejected the DOJ's claims that Google monopolized "advertiser ad networks," noting that this term itself "is not common in the digital advertising industry" and that the government's definition would "unduly exclude the publisher-facing side of two-sided ad networks."34 The case now moves to the remedies phase, where the DOJ is expected to push for structural changes that could potentially include forcing Google to sell off parts of its ad tech business.56

Google's dominance in the publisher ad server market was a central focus of Judge Brinkema's ruling. According to the court, Google's DoubleClick for Publishers (DFP) has maintained a staggering 84-90% market share over the last decade1. This overwhelming control was protected by high barriers to entry and significant switching costs that effectively trapped publishers in Google's ecosystem, even when the company degraded features or made changes publishers disagreed with1.

The court found that Google's monopolistic practices included tying its publisher ad server (DFP) to its ad exchange (AdX) through both contractual policies and technological integration2. This forced publishers to use Google's ad exchange if they wanted access to its ad server, artificially limiting competition. Even Meta abandoned its project to build a competing publisher ad server due to these significant barriers1. Google further cemented its dominance through anticompetitive "First Look" and "Last Look" policies that gave its own exchange preferential treatment in ad auctions3, allowing it to maintain a 20% "take rate" despite competitors offering lower prices4.

The court specifically identified Google's illegal tying of its ad exchange (AdX) to its publisher ad server (DFP) as a key anticompetitive practice. Google effectively forced publishers to use DFP if they wanted access to real-time bidding with AdWords advertisers, a crucial feature of AdX.12 This tying arrangement allowed Google to maintain a dominant position in both markets, with AdX handling between 54% and 65% of total transactions—approximately nine times larger than its closest competitor.13

Judge Brinkema found that Google exercised "coercive power" through this tying practice, violating both Section 1 of the Sherman Act (prohibiting unreasonable restraints on trade) and Section 2 (contributing to monopoly power).2 The court rejected Google's defense that these were legitimate product design choices, determining that Google's justifications of improved safety, privacy, and reduced fraud were either pretextual or substantially outweighed by the anticompetitive effects.3 As one Google internal communication described it, this was comparable to "Goldman or Citibank own[ing] the NYSE [i.e., the New York Stock Exchange]."1