Google Ad Tech Antitrust Ruling Forces Open Auctions and New Limits on Google’s Conduct

Judge Leonie Brinkema rejected the Justice Department’s request to break up Google’s advertising technology business, while imposing sweeping changes to AdX, DFP and AdWords that will reshape the open web advertising market for at least six years.

Google’s landmark ad tech antitrust case has entered its most consequential phase. In a 106-page remedies opinion, U.S. District Judge Leonie Brinkema imposed a broad package of behavioral remedies designed to restore competition in the markets for open web display publisher ad servers and ad exchanges. Google will retain ownership of its AdX exchange and DFP publisher ad server, but the company will have to open those systems to rival technology, provide publishers with substantially greater access to auction data, disclose how DFP selects winning ads, and restrict the ability of AdWords to favor Google’s own advertising infrastructure. The rules will apply worldwide and remain in force for six years, with an independent monitor and a technical committee overseeing compliance. 

The remedies follow Judge Brinkema’s April 2025 decision finding that Google violated Sections 1 and 2 of the Sherman Act by acquiring and maintaining monopoly power in two interconnected advertising technology markets. The court found that Google unlawfully tied DFP, its dominant publisher ad server, to AdX, its advertising exchange, and then reinforced that position through policies and technological features that disadvantaged competing exchanges and limited publishers’ ability to choose alternative products. The Justice Department later sought structural relief that would have required Google to divest AdX, open-source portions of DFP’s auction logic and potentially sell additional assets if competition failed to recover. Judge Brinkema declined to order a breakup, concluding that structural relief would be difficult to implement and could take years to complete. Instead, she chose a set of operating restrictions intended to change the way Google’s ad tech products interact with rivals and customers on a much shorter timetable.

Those restrictions are meant to weaken the historic relationship between AdX and DFP. Google will be barred from recreating mechanisms such as First Look and Last Look, which the court found had given AdX advantages over competing exchanges, and it must discontinue Unified Pricing Rules for indirect transactions. The court also prohibited Google from adopting policies or contractual arrangements that recreate the unlawful tie between its publisher ad server and exchange under a different name or technical structure. Rather than simply ordering Google to stop specific historical practices, the decree is designed to change the incentives and economics of the auction environment itself and make it easier for publishers to direct business toward competing ad tech providers.

According to the decision, Google must also build an application programming interface that allows Prebid, the widely used open-source header bidding technology, to obtain real time AdX bids for indirect open web display inventory. Google is further required to create an API and server to server connection between DFP and Prebid, while rival publisher ad servers will gain the ability to obtain real time AdX bids directly. For years, Google’s unique advertising demand was one of the strongest reasons publishers remained tied to Google’s broader ecosystem. Publishers that wanted access to AdX and the advertiser demand flowing through it had powerful incentives to use DFP as their publisher ad server. By requiring Google to make AdX demand available through competing infrastructure, the court is attempting to reduce that dependency and allow publishers to assemble their advertising technology stack from multiple providers. The opinion reflects the court’s view that genuine competition requires rivals to have practical access to the demand and data that historically made Google’s products so difficult to replace.

For advertisers, the court’s treatment of AdWords is particularly significant. Google argued that remedies involving its advertiser buying tools extended beyond the markets in which the government had established liability, but Judge Brinkema rejected that position with respect to AdWords because the liability record showed that its demand played a central role in sustaining Google’s ad tech structure. The court found that Google had effectively restricted the distinctive advertising demand generated by AdWords to AdX, giving publishers another reason to remain inside Google’s ecosystem. Judge Brinkema described AdWords demand as a major source of Google’s power in the ad exchange market and an important factor supporting DFP’s dominance in publisher ad serving. The remedy therefore reaches directly into the way AdWords participates in open web display advertising. Google will be prohibited from creating direct bidding integrations between AdWords and DFP for indirect open web display inventory, and AdWords may not favor AdX or another Google owned advertising product simply because Google owns it. 

The court also imposed new transparency requirements aimed at one of the recurring criticisms of Google’s advertising ecosystem, which is the limited visibility publishers historically had into DFP’s auction process. Google must provide technical documentation explaining how its final auction works and give publishers access to data showing what happened when individual ads were selected. That information is expected to include candidate prices, direct deal prices, programmatic bids, bid adjustments and the categories of adjustments applied. Publishers should therefore be able to examine the information considered by DFP and better understand why a particular advertisement won. The decree also requires broader access to publishers’ own DFP and AdX bidding data. Combined with the new interoperability requirements, these provisions are intended to give publishers both the information and the technical freedom needed to compare competing exchanges, identify potentially discriminatory treatment and move business toward other providers when those providers offer better economics.

The scope of the decree is unusually broad. Judge Brinkema concluded that the relevant publisher ad server and ad exchange markets are global and that Google operates its advertising technology on a global basis, so the final judgment will apply worldwide. The court selected a six-year term, rejecting DOJ’s request for 15 years while leaving open the possibility of an extension if the remedies have not been fully implemented. Compliance will be supervised by an independent monitor and a three-member technical committee, with Google responsible for their reasonable costs. The monitor will investigate complaints, review Google’s compliance and report to the court, while the technical committee will provide the specialized engineering expertise needed to evaluate APIs, data sharing systems and other technical obligations. The September order resolved the substance of the remedies and directed the parties to submit a proposed final judgment reflecting the court’s rulings, which means the precise operative language of the decree will be embodied in the final judgment entered by the court.

Judge Brinkema’s remedy ultimately preserves Google’s ownership of AdX and DFP while changing many of the mechanisms that allowed those products to reinforce one another. Google has indicated that it disagrees with the underlying liability ruling and intends to pursue further appellate review, so litigation over the case will continue. Even so, the remedies opinion marks a major development in the broader Google antitrust story because the court has moved from identifying unlawful market power to prescribing how Google’s advertising systems must interact with customers and competitors going forward. For advertisers, publishers and businesses considering Google Ads antitrust recovery, the record now contains detailed judicial findings concerning monopoly power, tying, auction design, preferential access, interoperability, transparency and the role of AdWords demand in sustaining Google’s advertising technology ecosystem.