A federal judge has ruled that Google illegally maintains monopolies in digital advertising technology, opening the door for a potential forced breakup of the tech giant’s advertising business.

Top Takeaways

• U.S. District Judge Leonie Brinkema found Google guilty of maintaining illegal monopolies in publisher ad servers and ad exchanges
• The ruling allows the Justice Department to seek breaking up Google’s advertising business in an upcoming remedy phase
• Google plans to appeal part of the decision while Alphabet’s shares fell 1.2% following the ruling
• This is Google’s second major antitrust loss after being found to have an illegal monopoly in the online search market
• The DOJ argues Google takes up to 35 cents per dollar spent on its advertising platforms, harming publishers and consumers

Google Found Guilty of Ad Tech Monopolies

U.S. District Judge Leonie Brinkema ruled on Thursday that Google illegally dominated two critical markets for online advertising technology. The decision stated that Google maintains monopoly power in both publisher ad servers and ad exchanges, substantially harming customers, rivals, and ultimately consumers. This verdict represents a significant victory for the Department of Justice in its ongoing efforts to curb the power of tech giants. The ruling specifically noted that Google’s extensive control over these advertising platforms allowed it to manipulate the digital advertising marketplace to its advantage.

The court rejected Google’s defense that the case focused primarily on past practices and failed to acknowledge increasing competition from other major tech companies like Amazon and Comcast. Judge Brinkema’s ruling was unequivocal about how Google had systematically built and maintained its monopolies. “Google further entrenched its monopoly power by imposing anticompetitive practices on its customers and eliminating desirable product features,” wrote Judge Brinkema in her decision, which detailed numerous ways Google leveraged its dominant position to disadvantage competitors and control the advertising ecosystem.

BOOM: Google loses ANOTHER antitrust suit, it's a monopolist of the software used by publishers to manage online ads, as well as the exchanges used to buy and sell online ads. pic.twitter.com/5bstcP50PN

— Matt Stoller (@matthewstoller) April 17, 2025

Potential Breakup of Google’s Ad Business

The ruling opens the possibility for dramatic remedies, potentially forcing Google to sell significant parts of its advertising business. The Justice Department has already suggested Google should divest its Google Ad Manager, which includes both its publisher ad server and ad exchange – core components of its digital advertising empire. Legal experts consider a breakup of Google’s digital advertising business increasingly likely following this decision. The court will determine the exact remedies during a second phase of the trial, where both sides will present arguments about appropriate corrective measures.

“This ruling is an unequivocal win for the American people that will help lower prices, increase competition, and lead to a better internet for everyone,” said Sacha Howarth, executive director of the Tech Oversight Project, following the decision.

Google’s response indicates the company is preparing for a protracted legal battle. “We won half of this case and we will appeal the other half,” stated Lee-Anne Mulholland, a Google representative. The company disputed the findings regarding its publisher tools, arguing that “Publishers have many options and they choose Google because our ad tech tools are simple, affordable and effective.” Despite Google’s defense, Alphabet’s shares fell 1.2% immediately following the announcement of the ruling, reflecting investor concerns about potential business impacts.

Broader Implications for Big Tech Regulation

This case represents the second major antitrust blow to Google, following an earlier ruling that found the company maintained an illegal monopoly in the online search market. The combined effect of these cases signals increasing regulatory pressure on large technology companies. DOJ attorneys argued during the trial that Google abuses its market power by extracting up to 35 cents per dollar spent on its advertising platforms – a rate they claim would be impossible in a truly competitive marketplace. The ruling also noted that Google’s monopolistic practices have particularly harmed publishers, who have seen diminishing returns from online advertising.

Beyond the immediate case, Google faces additional antitrust challenges. A separate trial in Washington will address the Justice Department’s request for Google to sell its Chrome browser and alter its online search dominance. The company has previously considered selling its ad exchange to satisfy European antitrust regulators, indicating increasing global pressure on its business model. A briefing schedule and hearing date will be set to determine specific remedies for these antitrust violations, with outcomes that could fundamentally reshape the digital advertising landscape.