Judge orders Google to open ad tech auctions to rivals under a six-year monitor

A federal judge has ordered Google to loosen its grip on the machinery that decides which advertisements appear on websites around the world, while declining to break the company apart. On September 16, 2026, U.S. District Judge Leonie Brinkema unsealed a 106-page opinion requiring Google to stop forcing publishers that use its DFP ad server to also route their auctions through its AdX ad exchange, to connect both products to the competing open-source Prebid framework, and to share real-time data on winning and losing bids with publishers. A compliance monitor will watch the company for six years.

The decision lands more than three years after the Department of Justice sued Google in 2023, and about 17 months after Brinkema found on April 17, 2025 that the Alphabet unit had violated antitrust law and wielded monopolistic power over some online advertising technology. That liability finding set up a separate remedy phase in which the government asked the court to force a sale of AdX, the exchange where publishers pay a 20% fee. Brinkema rejected that request.

Instead of divestiture, the judge described behavioral fixes that she said would "effectively pry open to competition the ad tech markets that were injured by Google's unlawful conduct, and prevent Google from reverting to anticompetitive conduct in these markets." The case was heard in the U.S. District Court for the Eastern District of Virginia in Alexandria, Virginia.

Google said it disagreed with Brinkema's liability ruling on its Google Ad Manager publishing tool and will appeal, arguing a breakup would hinder small businesses. The Department of Justice framed the outcome as a victory even though its central demand was denied.

Key Facts

Reuters reported on September 16 that the judge concluded Google should relax its rules governing online advertising auctions and appoint an internal antitrust compliance monitor, while stopping short of demanding that the Alphabet unit break up its advertising technology monopoly. The same report noted that Associate Attorney General Stanley Woodward Jr. called the decision a "significant victory" in Justice Department efforts to protect and restore competition.

The Next Web reported on September 17 that the changes will remain in place for six years, the term Google itself proposed, instead of the 15 years sought by the Department of Justice and the states that joined the case. The outlet noted that Brinkema had ruled on September 2, 2026 that Google would not have to sell AdX. The court can extend the period if the judgment has not achieved its goal. The rules apply worldwide, and the requirements take effect within 60 days.

Courthouse News Service reported on September 16 that the unsealed memorandum sets out a Monitor and Technical Committee to oversee compliance, a ban on discriminatory bidding, and an order that Google integrate its ad exchange with rival publisher ad servers. Both Google and the Justice Department had proposed establishing a monitor and technical committee, the outlet noted.

The core structural change breaks the link between Google's two main publisher tools. Websites that use the DFP ad server will no longer have to use AdX, and AdX must bid into rival publisher ad servers on the same terms it offers DFP. Google must also connect AdX and DFP to Prebid, the open-source header-bidding framework publishers adopted to obtain competing bids outside Google's control, and it must publish documentation explaining how DFP picks auction winners. Brinkema rejected a demand to open-source DFP's auction code and turned down the government's push to force a sale of AdX, where publishers pay a 20% fee.

The financial stakes are substantial. According to the judge's decision, annual global digital advertising spending could grow to $605 billion next year from $424 billion in 2023. Advertising accounted for about 73% of Alphabet's revenue last year, and the company's market value exceeds $4.1 trillion. NewsDive reported on September 17 that the ruling lets Google avoid divesting another part of its advertising empire as it races to expand in artificial intelligence against companies such as Anthropic and OpenAI.

Analysis

The most revealing passage in the 106-page opinion is the judge's explanation of why she refused to order a sale of AdX. The Justice Department's "rationale for seeking divestiture boils down to a lack of trust that Google will comply with an order from this court and an unrealistic desire for certainty," Brinkema wrote. She chose supervision plus specific conduct rules over structural separation, adding that her remedies "will be sufficient to effectively pry open to competition the ad tech markets that were injured by Google's unlawful conduct."

What this really means is that the United States has now answered the central question in its biggest advertising antitrust case with a promise to watch rather than a mandate to split. The government won a liability finding in April 2025 and a set of worldwide conduct rules in September 2026, but it lost the remedy that would have permanently removed AdX from Google's ownership. Enforcement will instead rest on a monitor whose precise powers are still described inconsistently in the public record. Reuters reported that Google should appoint an internal antitrust compliance monitor, while AdExchanger described a court-appointed technical monitor with full access to Google's staff, systems and source code.

The six-year term compounds the uncertainty. Even the judge acknowledged distrust of the defendant, referring to a "lack of trust that Google will comply with an order from this court." A company that intends to appeal the underlying liability ruling has obvious incentives to litigate, delay and narrow whatever the monitor can see, and the shorter window gives it less time to outlast but also less time for the market to reorder itself around the new rules.

Not everyone accepts the behavioral approach. Barry Lynn of the Open Markets Institute called the decision "more proof the U.S. judiciary is abdicating its congressionally mandated duty to apply antitrust laws." The counterargument, implicit in Brinkema's opinion, is that a worldwide injunction covering auction mechanics, bid data and product integration may change daily behavior faster than a divestiture that would take years to execute and could be undone by the market power of the remaining pieces.

Why It Matters

Advertising is not a side business for Alphabet. Advertising accounted for about 73% of the company's revenue last year, and its market value exceeds $4.1 trillion. The ad tech layer that Brinkema scrutinized sits between publishers and advertisers, deciding in milliseconds which bid wins and at what price. When the same company owns the ad server used by publishers, the exchange where those impressions are sold and the tools advertisers use to buy them, small changes in auction rules move real money. Opening AdX to rival ad servers and to Prebid, and forcing disclosure of how DFP picks winners, attacks that advantage directly.

The projected growth of the market explains the urgency on both sides. Global digital advertising spending could rise to $605 billion next year from $424 billion in 2023, according to the decision. A 20% publisher fee on an exchange of that scale is worth fighting over, and it is why the Justice Department wanted AdX sold outright rather than merely regulated. Brinkema's answer was that access to real-time bids from AdX through other publisher ad servers would restore "much-needed" competition.

The ruling also matters beyond the United States because the injunction applies worldwide. Google had argued that a U.S. court should not impose an injunction operating outside the nation's borders, but Brinkema disagreed, writing that a worldwide application would entail product changes that are consistent across all regions and in line with Google's current operations.

Next Up

Attention now shifts to implementation. The requirements take effect within 60 days, which means Prebid integration, real-time bid reporting and documentation of DFP auction logic must move from opinion to product while Google pursues an appeal of the liability ruling on its Google Ad Manager publishing tool. The Monitor and Technical Committee must also be constituted, and how much access it receives to staff, systems and source code will determine whether the six-year term means anything.

If the final judgment is not fully satisfied, the court has the authority to extend it, a lever that keeps pressure on Google long after September 16, 2026. Regulators and publishers will be watching whether rival ad servers actually receive AdX bids on the same terms as DFP, and whether the next round of litigation reshapes a remedy that the judge herself framed as a test of Google's willingness to comply.