On September 9, 2024, the U.S. Justice Department told a federal judge that Google controlled three connected layers of the open-web advertising system: publisher ad servers, ad exchanges, and advertiser ad networks. DOJ attorney Julia Tarver Wood called the alleged structure a “trifecta of monopolies.”
That phrase described the government’s opening argument—not the final judgment. In an April 17, 2025 ruling, Judge Leonie Brinkema found Google liable for monopolizing the publisher ad-server and ad-exchange markets and for unlawfully tying AdX to DFP. The court dismissed DOJ’s advertiser-ad-network monopolization count.
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What happened on the first day of the trial?
The ad-tech antitrust trial began September 9, 2024, in the U.S. District Court for the Eastern District of Virginia before Judge Leonie Brinkema. The case, United States et al. v. Google LLC, was filed by the Justice Department and state plaintiffs in January 2023.
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In its opening statement, DOJ argued that Google had assembled control over the principal technical layers used to buy and sell advertising on the open web. Google disputed that description, arguing that the government had defined the market too narrowly and excluded major channels such as mobile apps, social media, connected television and retail media.
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The central question was not simply whether Google was large. Under U.S. antitrust law, DOJ had to establish relevant markets, show that Google possessed monopoly power in them, and prove that Google maintained that power through exclusionary conduct rather than through ordinary competition or better products.
DOJ’s case was separate from the Justice Department’s search-antitrust lawsuit filed in 2020.
Read the Justice Department’s case materials.
What is the ad-tech stack?
“Ad tech” refers to the software and marketplaces that automate the purchase and sale of digital advertising. A simplified transaction works like this:
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1Fix the driver behind crashes, sound loss and screen glitches2Repair Windows errors before they cause bigger problems3Scan for outdated or missing drivers - takes under a minute- A publisher—such as a news website—has an available advertising space, or impression.
- The publisher’s ad server manages that inventory, applies rules and direct-sale commitments, and determines how the impression can be offered.
- An ad exchange conducts an automated auction, often in milliseconds.
- Advertiser-side tools submit bids for the opportunity to show an ad.
- The winning advertisement is delivered to the user.
DOJ’s theory focused on Google’s presence at several points in that chain. The government said that owning important tools for publishers, exchanges and advertisers gave Google more influence over access, auction rules, data and fees than a company competing at only one layer would have.
| Market layer | What it does | Google product identified by DOJ |
|---|---|---|
| Publisher ad server | Manages advertising inventory, rules and sales opportunities | DoubleClick for Publishers, later Google Ad Manager |
| Ad exchange | Runs automated auctions matching inventory with advertiser bids | Google AdX |
| Advertiser ad network | Connects advertisers with available advertising inventory | Google Ads |
The stack is sometimes discussed alongside demand-side platforms and supply-side platforms. Those tools also help advertisers and publishers participate in automated advertising, but the government’s three alleged markets were specifically the publisher ad-server, ad-exchange and advertiser ad-network markets.
What were the three alleged monopolies?
1. The publisher ad-server market
A publisher ad server helps a website organize available ad space, manage direct advertising agreements, set priorities and connect inventory with buyers.
DOJ identified Google’s DoubleClick for Publishers, or DFP, later known as Google Ad Manager, as the dominant publisher-side product. According to the government’s complaint, DFP had more than 90% share in the relevant market. That figure was DOJ’s allegation based on its market definition, not an uncontested measure of every publisher’s advertising software.
2. The ad-exchange market
An ad exchange is a marketplace where advertising impressions are offered to potential buyers and bids are compared. The auction can happen in a fraction of a second while a webpage loads.
DOJ alleged that Google AdX was the largest exchange and represented at least 50% of the relevant market under the government’s definition. The government argued that Google used its position to limit rivals’ access to publisher inventory and to influence how auctions operated.
3. The advertiser ad-network market
An advertiser ad network helps businesses buy display advertising and reach available audiences. DOJ identified Google Ads as a major tool used by both small and large advertisers.
The complaint described Google Ads as holding roughly 80% of the relevant advertiser-ad-network market. Again, that was a government allegation about a defined market—not a claim that Google handled 80% of all advertising worldwide or even all digital advertising.
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The government’s theory involved Google’s business structure and several alleged practices.
Acquisitions
DOJ pointed to Google’s acquisition of DoubleClick in 2008 and AdMeld in 2011. The government argued that these transactions helped Google expand across the advertising transaction and consolidate important positions on both the publisher and exchange sides.
Tying and conditioning
DOJ alleged that Google tied or conditioned access to valuable exchange demand and functionality on the use of Google’s publisher tools. In practical terms, the government argued that publishers could face disadvantages if they tried to separate Google’s ad server from Google’s exchange.
Restrictions on auction participation
The government alleged that Google limited rivals’ access to real-time bidding opportunities and restricted the ways competing tools could interact with Google’s systems.
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Favoring Google’s own products
DOJ also alleged that Google altered auction mechanics or applied rules in ways that favored its own products. The broader concern was that Google could influence both the rules governing an auction and the products competing within it.
Data, scale and fees
The government argued that activity across the stack produced data and scale advantages that competing vendors could not easily replicate. DOJ also said Google kept, on average, more than 30% of advertising dollars flowing through its ad-tech products. That was an average across transactions and customers—not a claim that Google charged exactly 30% on every ad dollar.
See DOJ’s complaint announcement and market allegations.
How did Google respond?
Google’s opening argument was more than a general denial. Its defense attacked the government’s market definitions, evidence and theory of harm.
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Scan for outdated or missing drivers - takes under a minuteDriver Scan →Repair Windows errors before they cause bigger problemsFix Now →- The markets were too narrow. Google argued that DOJ focused on open-web display advertising while excluding mobile apps, social platforms, connected television, retail-media networks and other growing channels.
- Advertisers and publishers had alternatives. Google pointed to companies including Microsoft, Amazon, Meta and TikTok as competitors investing in advertising.
- Integration could improve efficiency. Google’s position was that connected products could reduce latency, lower costs and work more effectively together.
- Fees were not proof of unlawful monopoly power. Google disputed DOJ’s characterization of its fees and argued that comparisons with other industry participants did not establish illegal conduct.
- Remedies could harm customers. Google warned that forced separation or restructuring could make advertising less efficient and hurt publishers and advertisers.
The market-definition dispute was especially important. A company can be dominant in a legally defined market without controlling every type of advertising. The court therefore had to decide which products and transactions belonged in the relevant markets, not whether Google competed with every advertising business in the economy.
Why did the case matter to publishers?
Publishers use advertising to fund articles, videos and other content. DOJ argued that Google’s position could reduce the money publishers ultimately receive by increasing fees, weakening competition among exchanges or making rival tools less effective.
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The government also argued that integration, switching costs, access to advertiser demand and product compatibility could make it impractical for many publishers to move away from Google, even if alternatives technically existed.
That does not mean every publisher was forced to use Google or that every publisher paid the same fee. The more precise issue was whether Google’s control and business practices made competing systems less attractive or less viable than they would have been in a more open market.
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Why did it matter to advertisers?
Advertisers sit on the other side of the transaction, but they can still be affected by the structure of the ad market. Less competition among buying tools could mean higher costs, fewer choices and less transparency about how bids are evaluated.
Advertisers may also care about whether an independent intermediary is handling a transaction or whether one company supplies tools to both the buyer and the seller. DOJ argued that control across both sides could create conflicts of interest and reduce the ability of advertisers to evaluate whether auctions were operating fairly.
These effects are not identical for every advertiser. A large brand, a small business buying through Google Ads and an agency using several platforms may experience the market differently. The government’s broader claim was that reduced competition could affect pricing, access to audiences and the amount of advertising money reaching publishers.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.What did the court ultimately decide?
The April 17, 2025 ruling did not uphold DOJ’s complete “trifecta” framing. Judge Brinkema found Google liable for:
- Monopolizing the publisher ad-server market;
- Monopolizing the ad-exchange market; and
- Unlawfully tying AdX to DFP.
The court dismissed DOJ’s advertiser-ad-network monopolization count. As a result, it is inaccurate to say that Google was found to have monopolized all three markets identified in DOJ’s opening statement.
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The distinction matters. “Trifecta of monopolies” accurately describes the government’s Day 1 allegation and opening theory. It is not an accurate summary of the court’s complete liability ruling.
Read the April 17, 2025 memorandum opinion.
What happened after the liability ruling?
The case moved into remedies proceedings. DOJ sought structural changes to Google’s ad-tech business, including relief addressing the relationship between Google’s publisher ad server and exchange.
The Justice Department’s case page lists a remedies hearing beginning September 22, 2025, along with proposed orders, post-trial briefs and related filings. The page also showed continuing litigation and compliance-related materials as of August 18, 2026. The existence of those filings does not, by itself, establish that a final remedy has been ordered. Readers should consult the court docket or the DOJ case page for the latest procedural development.
The broader issue: efficiency or exclusion?
The case presented two competing explanations for Google’s integrated ad-tech business.
DOJ argued that control across several connected layers allowed Google to favor its own products, restrict rivals, influence auction rules and extract excessive fees. In that view, the integration was not merely a convenience; it was a structure that could prevent effective competition.
Google argued that integration could create legitimate efficiencies. Products designed to work together may reduce delays, simplify transactions and lower operating costs. A successful product or acquisition is not automatically unlawful simply because it becomes widely used.
The legal question was whether Google used its market position to exclude competition unlawfully. That required more than proving that Google had many customers, high market shares or popular advertising products.
The practical stakes extend beyond Google. The outcome could affect publisher revenue, advertiser costs, independent ad-tech companies, auction transparency and the economics of the open web. It could also influence how regulators evaluate vertically integrated technology companies that operate both marketplaces and the tools used by participants in those marketplaces.
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