Google's Ad Monopoly Ruling: What Changes for Advertisers

March 2026 | Croupier Blog

In April 2025, Judge Leonie Brinkema issued a 115-page ruling finding Google liable for illegally monopolizing the publisher ad server market and the ad exchange market. She found that Google's conduct had "substantially harmed" publishers and "ultimately, consumers of information on the open web."

This is the second antitrust loss for Google in under a year. In August 2024, Judge Amit Mehta ruled Google illegally monopolized search. In September 2025, he imposed behavioral remedies — banning exclusive default search engine contracts and requiring Google to share search index data with rivals.

The ad tech case is more consequential. The DOJ is pushing for divestiture of Google's ad exchange (AdX) and publisher ad server (DFP). Closing arguments on remedies wrapped in November 2025. A decision is expected in 2026.

What Google Was Found Guilty Of

Two of three counts stuck:

  1. Monopolizing the publisher ad server market. Google's DoubleClick for Publishers (DFP) serves the majority of publisher ad inventory online. Google used its dominance to force publishers into using AdX for exchange services.

  2. Unlawfully tying DFP to AdX. Publishers who wanted the best ad server also had to use Google's exchange. This locked out competing exchanges and gave Google a guaranteed cut of every transaction.

The third count — monopolizing the advertiser ad network — was dismissed for failure to define a relevant market.

The Numbers Behind the Monopoly

During the trial, Google's own executives acknowledged that AdX extracted "irrationally high rents." Internal documents showed Google knew its exchange wasn't competitive on price but maintained market share through tying.

The economics are straightforward. Google sits in the middle of most programmatic transactions:

Google takes a cut at each layer. The ANA found that only 36 cents of every programmatic dollar entering a DSP reached consumers. Google's take rate on AdX was estimated at 20% or more per transaction.

When one company controls the buyer's tool, the seller's tool, and the marketplace, price discovery breaks down. The middleman sets the spread.

What Divestiture Would Mean

If the DOJ gets its way, Google would be forced to sell AdX and DFP as separate entities. This would:

For publishers: Open up the ad server market to competition. Publishers could choose an ad server without being locked into a specific exchange. Real competition on take rates becomes possible.

For advertisers: Create transparency into exchange pricing. When the exchange is independent from the ad server and the DSP, each layer has to compete on its own merits.

For the open web: Reduce the structural advantage of walled gardens. When a single company can steer ad dollars to its own properties (YouTube, Search) over the open web, independent publishers suffer. Divestiture breaks that steering mechanism.

What It Doesn't Fix

Breaking up Google's ad infrastructure addresses market structure, not measurement. Even in a post-divestiture world, advertisers still face the same attribution problem: the platform selling the impressions reports on their performance.

A divested AdX still reports its own numbers. A divested DFP still counts its own impressions. The conflict of interest shrinks but doesn't disappear.

The deeper fix is advertiser-side measurement — attribution that the advertiser controls. Cryptographic coupons give the advertiser their own signed tokens to track which channels actually convert. No platform dashboard. No self-reported metrics. The advertiser counts their own receipts.

What Advertisers Should Do Now

  1. Diversify your ad infrastructure. If divestiture happens, new ad servers and exchanges will compete for your business. Start evaluating alternatives now.
  2. Demand placement transparency. Google enabled full placement reporting for the Search Partner Network in August 2025. Push for the same in Performance Max.
  3. Build independent measurement. Don't wait for regulators to fix attribution. Run parallel campaigns with cryptographic tokens to establish your own conversion baselines.

The antitrust ruling creates space for competition. But competition only helps if advertisers have independent measurement to compare options. The monopoly wasn't just in infrastructure — it was in information.

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