Privacy & regulation · also called Competition law in ad tech
Antitrust in ad tech
Antitrust in ad tech refers to competition-law cases and investigations examining whether dominant companies, especially Google, have monopolised or abused their position in the technology used to buy and sell ads.
Ad tech is a natural target for competition authorities: a few firms operate on both the buy and sell sides and run the auctions in between, creating potential conflicts of interest. The central question is whether dominance has let a company raise its take rate, exclude rivals or disadvantage publishers and advertisers.
The most important case is United States v. Google, in which a US federal court ruled in April 2025 that Google had unlawfully monopolised the publisher ad server and ad exchange markets and illegally tied them together. In Europe, France's competition authority fined Google €220 million in 2021 over ad tech self-preferencing, and in September 2025 the European Commission fined Google €2.95 billion for abusing its dominance in ad tech. Canada's Competition Bureau also sued Google over ad tech in 2024, and the UK's CMA has investigated.
Competition rules also shape platform privacy moves: the Privacy Sandbox was supervised by the UK CMA, Apple's App Tracking Transparency has been examined by several regulators, and the EU's Digital Markets Act builds competition obligations into law for gatekeepers.
Think of it like this
Ad tech antitrust is like asking whether one company can fairly own the auction house, represent the sellers, advise the buyers and set the rules of the bidding all at once.
An example
After the EU's September 2025 decision, Google was ordered to end the self-preferencing practices the Commission identified, while in the US the ad tech remedies phase continued through 2026.
Related terms
United States v. Google (ad tech)
United States v. Google (ad tech) is the US Justice Department's antitrust case in which a federal court ruled in April 2025 that Google illegally monopolised key open-web ad tech markets.
Digital Markets Act (DMA)
The Digital Markets Act (DMA) is an EU regulation imposing competition-style obligations on designated "gatekeeper" tech platforms, including limits on combining personal data for ads without consent.
Publisher ad server
A publisher ad server is the system a website, app or streamer uses to manage its ad inventory and decide, for every ad slot, which campaign or programmatic buyer gets the impression.
Ad exchange
An ad exchange is a digital marketplace where buyers and sellers of ad impressions meet and trade through automated auctions, usually in real time.
Take rate
Take rate is the percentage of the money flowing through an ad tech platform that it keeps as its fee: platform revenue divided by the gross spend it handles.
Sources: US DOJ: Department of Justice prevails in landmark antitrust case against Google (April 2025), US DOJ: Justice Department sues Google for monopolizing digital advertising technologies (January 2023), European Commission: Digital Markets Act