This week, the U.S. Department of Justice initiated closing arguments in its historic case against Google, seeking to break up the world’s largest digital advertising ecosystem in a trial that could redefine the landscape of online commerce, publishing, and technology for years to come.
How Did We Get Here? Background and Ruling
On September 22, 2025, Judge Leonie Brinkema of the U.S. District Court for the Eastern District of Virginia began hearing arguments on remedies for Google’s unlawful monopoly in the ad tech sector. Earlier this year, Judge Brinkema ruled that Google had illegally maintained a monopoly over the tools websites use to sell digital ad space, and the software that connects those publishers with advertisers looking to buy.
In her decision, Brinkema found that Google unlawfully tied together its publisher ad server (DFP) to its ad exchange (AdX), leveraging its dominance to stifle competition in display advertising. “Google’s solutions were tailored, as law requires, to the technology in the case at hand and the complexity of the ad tech system,” said Karen Dunn, Google’s lawyer. The government disagreed: Nothing short of a structural divestment is sufficient to bring meaningful change, countered DOJ lawyer Julia Tarver Wood.
What’s at Stake? Billions, Innovation—and the Future of Digital Ads
Google’s ad tech system controls an estimated 87% of the publisher-side ad serving market in the United States, allowing it to extract up to 20% fees on every auction, according to DOJ arguments. The digital ads industry is now valued at $305 billion annually. Testimony showed publishers’ ad revenues have stagnated, while Google’s ad business doubled to $30 billion in a decade.
Publishers, represented by witnesses such as Grant Whitmore of Advance Local, insisted a breakup is needed for true competitive balance: breaking up the pieces of Google’s ad tech supply chain would offer the ability to get to a more level playing field. Andrew Casale, president of Index Exchange, echoed: Google’s proposals to share data and open up its technologies would not be enough to restore competition in the field.
What Will the Court Decide?
The DOJ argues that Google must sell off critical pieces of its ad tech business, specifically the AdX exchange and possibly the DoubleClick publisher ad server. This would, the DOJ says, prevent Google from unfairly favoring its own products and create space for true rivals.
Google’s lawyers, meanwhile, propose opening their software to competitors and making technical adjustments, warning that forced divestiture is radical and reckless and could disrupt the advertising ecosystem and reduce market stability.
Broader Implications: Tech Giants Under Scrutiny
This isn’t the only front in the government’s fight against tech monopolies. The DOJ has active cases against other giants, including Meta, Amazon, and Apple, and recently concluded another Google search monopoly trial.
Industry and Analyst Reaction
Industry observers note that many publishers and exchange competitors have seen business erosion as Google centralized market power. Lawsuits from companies like Business Insider and PubMatic seek compensation and demand more transparency in fees and data practices.
Meanwhile, European regulators have also brought antitrust cases against Google ad tech, influencing remedies and scrutiny worldwide.
What’s Next?
Judge Brinkema is expected to rule on remedies—potentially ordering Google to sell off core ad tech assets—within months. Google is likely to appeal any order for divestiture. As noted in coverage, the coming months will shape whether the government’s antitrust tools can actually dislodge tech giants’ hold over commerce and communications.
The U.S. v. Google ad tech case could be one of the most consequential antitrust battles of the digital era—reshaping not just Google, but the future rules of digital advertising and online competition.
