On 17 April 2025, Judge Leonie Brinkema of the U.S. District Court for the Eastern District of Virginia ruled that Google monopolised two digital advertising technology markets and unlawfully tied its publisher ad server (“DFP”) and its ad exchange (“AdX”). This marked a huge success for the U.S. federal government and 17 states who had brought the case. Having found Google liable, the Court will determine the appropriate remedies for these antitrust violations.
Today, the U.S. and the 17 states presented its proposes remedies in the case in a 17 page submission (which I will refer to as the Department of Justice’s (“DoJ”) proposal). The trial on remedies will commence on 22 September 2025.
In this blog post, we provide a short background to the judgment and remedies proposal, after which we dissect the proposal itself, turn to potential remedies the European Commission may impose, and conclude with the next steps to look out for in the (now) global enforcement against Google’s antitrust violations in ad tech.
Background
Display ads are shown on websites to visitors who browse the internet. For example, if someone visits the New York Times website, they will see a number of ads. These ads are dynamically placed: they are targeted at the specific visitor.
Several tools are a part of the automated ecosystem that powers this dynamic placement of ads (known as the “ad tech stack”). These include buy-side tools used by advertisers to buy digital ads, and sell-side tools such as publisher ad servers, a key tool for publishers to manage and sell their inventory. Ad exchanges, meanwhile, are the critical intermediary between advertisers’ ads and publishers’ inventory. They facilitate real-time auctions in which advertisers (through their tools) can bid on inventory. A detailed explanation of how these technologies work can be found in both the French Competition Authority’s (FCA) decision of 7 June 2021, and in the UK CMA’s online advertising market study final report.
Google owns key tools on all sides of the stack, with its publisher ad server DoubleClick for Publishers (DFP), its ad exchange AdX, and its advertiser tools Google Ads and DV360. Since the Google-owned ad exchange’s purpose is to optimise the allocation of advertiser demand and publisher supply, and Google represents both advertisers and publishers with its tools, there is an inherent conflict of interest. A senior manager at Google famously compared this to the unthinkable scenario where Goldman Sachs or Citibank would own the New York Stock Exchange.
As already established by the FCA decision of 2021 , Google’s DFP is dominant in the publisher ad server market. The FCA found that Google abused that dominant position because DFP gave preferential treatment to Google’s ad exchange (AdX) and, in turn, AdX gave preferential treatment to DFP.
In addition to the FCA decision, several other actions were brought against Google by U.S. states, the European Commission and the UK CMA. Those cases are all ongoing at present. Potentially the most pivotal public enforcement action was started relatively late, with the U.S. DoJ and 17 states filing their five-count complaint against Google in January 2023. However, that case progressed most quickly, and led to a final judgment in April 2025.
In her Memorandum Opinion, judge Leonie Brinkema found that the DoJ had succeeded in proving that Google monopolised the publisher ad server and ad exchange markets, and had unlawfully tied DFP and AdX. She dismissed the remainder of the DoJ’s case, finding that the DoJ had failed to prove that there is a relevant market for open-web display advertiser ad networks (which is on the advertiser side of the stack).
Google’s conduct spans a lengthy period of time and is set out in detail in the Memorandum Opinion of the Court. According to the Court it consists, among other things, of requiring publishers using DFP to offer AdX a first right of refusal for each impression (“first look”). This “artificially advantage[ed] AdX within DFP’s auction logic at the expense of Google’s publisher customers”. Publishers sought to improve competition between AdX and other ad exchanges by negating Google’s first look advantage (Opinion, at 32-33). They did so by introducing header bidding, which allowed for fair auctions for the publisher’s inventory to be held outside of Google’s tools, and then placing the winning bid in the header bidding auction into DFP as a floor price against which AdX would compete. In the words of the Court, “Google was wary of header bidding, seeing it as a risk to its revenue model that relied upon AdX having a real-time First Look at publisher inventory”. Google declined to have AdX participate in header bidding, choosing instead to implement new features and policy changes to counteract the growing threat of header bidding, and to strengthen the DFP-AdX tie.
The Court found that these included Google’s “last look”, which gave AdX the ability to see competing exchanges’ bids in an otherwise sealed auction before AdX would bid, and “dynamic revenue share”, where Google used its last look information advantage to vary AdX fees and win impressions that it would otherwise have lost in a fair auction. The crux of “Google’s decade-long campaign of exclusionary conduct” was its common control of DFP, AdX and AdWords, which allowed it to restrict the unique advertising demand offered by AdWords advertisers to AdX and to tie DFP to AdX.
The DoJ’s remedies proposal
Remedies in a U.S. antitrust case must meet four objectives: (1) “unfetter a market from anticompetitive conduct,” (2) “terminate the illegal monopoly,” (3) “deny to the defendant the fruits of its statutory violation,” and (4) “ensure that there remain no practices likely to result in monopolization in the future” (U.S. v Microsoft 253 F.3d 34, 103 (D.C. Cir. 2001)).
The DoJ is seeking a mix of structural, behavioural and administrative remedies to meet those four objectives. The most eye-catching proposed remedies are the divestiture of Google’s ad exchange AdX, and the phased divestment of its publisher ad server DFP. If accepted by the Court, these would be comprehensive and hard-hitting remedies, bringing to an end Google’s dominance in the ad tech stack.
Divestiture of AdX
According to the Court, the “primary source” of Google’s monopoly power in the ad exchange market was that it effectively restricted the unique advertising demand offered by AdWords advertisers to AdX, which made it more difficult to switch to rival exchanges. Further, the Court established that the DFP-AdX tie made AdX “the glue that sealed DFP inventory to AdWords demand”. The DoJ submits that AdX is a critical instrument of Google’s anticompetitive scheme. Furthermore, because Google unlawfully acquired monopoly power in the ad exchange market, that power is “among the fruits of its statutory violation”.
To accomplish the four objectives from the case-law, the DoJ is seeking the full divestment of AdX, which is to occur “as soon as possible”, overseen by a court-appointed trustee. In the interim, Google would be required to provide an API through which AdX will bid into header-bidding wrappers such as Prebid (an organisation formed by non-Google industry members and open-source advocates which developed header bidding), and have AdX bid into non-Google publisher ad servers in the same way in which it bids into DFP. Finally, Google would be prohibited from operating an ad exchange for a period of ten years.
Phased divestiture of DFP
Like AdX, DFP is an instrument of Google’s anticompetitive campaign, according to the DoJ. Given “Google’s decimation of competition in the publisher ad server market over the past 15 years”, the DoJ submits that DFP should be opens-sourced and divested. This open-sourcing and divestiture would occur in three phases:
- In phase one, Google must link up DFP to Prebid. Google would be required to provide an API and server-to-server connection for DFP to integrate with and receive bids from the Prebid header-bidding wrapper in the same way and on the same terms as DFP integrates and solicits bids from AdX. In addition, Google would be required to assist publishers in transferring their data from DFP to another publisher ad server.
- In the second phase, the Google would have to modify DFP to separate out the code that performs the final auction within the publisher ad server (that is, the “auction logic” that makes the ultimate decision on what ad to serve). Google would then submit that code under an open-source license to industry organisations and participants. Google would also be required to provide an API in DFP to allow another entity to host the final auction outside of DFP (this could be a neutral third-party industry organisation or another entity chosen by the publisher). On completion of this second phase, Google would be prohibited from hosting or recreating the final auction logic in any Google product.
- In phase three, Google would divest the remainder of DFP. This means the forced sale of the administrative functions of the ad server. The divestment would again be overseen by a court-appointed trustee, and the DoJ proposes that DFP not be divested to the same entity that acquires AdX. The DoJ also recognises that this third phase may ultimately not be necessary, and proposes a Court-supervised mechanism for evaluating competition in the publisher ad server market after completion of the second phase to test whether the first two phases and the other proposed remedies have restored competition by then.
Other remedies
The DoJ also proposes a series of behavioural remedies to prevent Google from engaging in similar conduct in the future, and to ensure competition is restored in the ad exchange and publisher ad server market. This includes, for example, that Google’s buyside tools (AdWords and DV360) deal with all third-party ad tech tools on non-discriminatory terms. The DoJ also wants the Court to order that Google place in escrow 50% of the net revenues from AdX and DFP from the date of the Court’s opinion (17 April 2025) until full divestment of AdX and DFP. Finally, the DoJ is seeking several data and transparency provisions to remedy Google’s data and scale advantages, monitoring proceedings and a prohibition on retaliation, and measures to deal with Google’s “systemic disregard of the evidentiary rules”.
Google will respond to the DoJ’s proposal on 19 May 2025. Following this, both parties will serve expert reports and replies, and the DoJ’s final proposed order reflecting the appropriate remedies in the case will be due on 5 September 2025. The trial before Judge Brinkema will commence on 22 September 2025. That means we could see a judgment before the end of the year, with remedies implementation starting in early 2026.
All eyes on the European Commission (at least until September)
The European Commission also raised potential structural remedies as a possibility in its press release announcing that it had issued a statement of objections in June 2023, stating that it was of the preliminary that “only the mandatory divestment by Google of part of its services would address its competition concerns”. While it did not go into any detail on what that would look like, it included the following image (source: European Commission).
There is bound to have been contact between the Commission and DoJ since the Commission’s June 2023 press release, so this image may be out of date. However, it is clear that the Commission is seriously considering structural remedies as well. It can now proceed to impose them, safe in the knowledge that its position is significantly strengthened by the DoJ publicly taking exactly the same view.
The Commission’s remedies power in Article 7 of Regulation 1/2003 is underdeveloped and has never been used to impose remedies as sophisticated as the ones outlined in the DoJ’s proposal. However, European competition law has arguably never encountered a situation similar to the one present in this case where the defendant is vertically-integrated across a whole tech stack filled with conflicts of interest. Given the Commission’s signalling in its June 2023 press release that it envisaged structural remedies, it can therefore be expected, particularly now that the Commission is emboldened by the U.S. Court’s judgment on liability and the DoJ’s remedies proposal, to pursue the necessary step of imposing a divestment order.
Indeed, now would be a good time to do so, as this would show a united front between the DoJ and Commission as apex competition enforcers, while also demonstrating that the Commission can act decisively in an era-defining case such as this one.
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