Google has announced its intention to appeal a U.S. court ruling that found the technology giant liable for maintaining an illegal monopoly in the online advertising technology market. The decision, handed down by U.S. District Judge Leonie Brinkema on Thursday, April 17, 2025, concluded that Google had "willfully acquiring and maintaining monopoly power" in the markets for publisher ad servers and ad exchanges.

The court's ruling was a mixed bag, however. Judge Brinkema determined that while Google's publisher tools did violate antitrust laws by hindering competition, the Department of Justice (DOJ) failed to demonstrate that Google's advertiser tools and acquisitions of DoubleClick and AdMeld were anticompetitive.

Google's response to the ruling has been firm, with the company stating its disagreement with the court's decision regarding its publisher tools. According to Google, publishers have numerous options available to them and choose Google's ad tech tools due to their simplicity, affordability, and effectiveness. Lee-Anne Mulholland, Google's vice president for regulatory affairs, stated that the company would appeal the portion of the case it did not win.

The lawsuit against Google, brought by the DOJ and a coalition of states, alleged that the company's dominance in ad tech allowed it to charge higher prices and seize a larger share of each sale. The DOJ had sought to compel Google to divest at least its Google Ad Manager, which encompasses the company's publisher ad server and ad exchange.

Judge Brinkema's decision highlighted that Google had illegally linked its publisher ad server to its ad exchange, effectively locking out competition regardless of the quality of competing products. The court found that Google had "willfully" maintained monopoly power, suggesting the company's actions went beyond simply having superior products.

This isn't the first time Google has faced antitrust scrutiny. The DOJ initially targeted Google's ad network in 2023, and the company has been involved in other antitrust cases, including one related to the Google Play Store.

The implications of the ad tech ruling are potentially far-reaching. The programmatic advertising market, which accounts for a significant portion of U.S. display ads, has become increasingly concentrated, with Google's tools occupying critical positions in the buying and selling process.

Historically, antitrust breakups have fostered innovation and the emergence of new market leaders. The Google ad tech ruling follows a pattern established by landmark antitrust cases that reshaped entire industries, benefiting consumers in the process.

The case now moves into a penalty phase, expected to begin later this year or early 2026. The Justice Department is likely to push for structural changes, potentially including forcing Google to sell off parts of its ad tech business—specifically, the Ad Manager platform and ad exchange. The resolution of this case and any potential remedies could significantly alter the landscape of the digital advertising industry.