Is Google Facing Another Breakup? U.S. Antitrust Focuses on the AdX Platform

TradingKey - After failing to force Google to divest its Chrome browser, the U.S. government is now concentrating its antitrust firepower on another major case: demanding that Google sell off its online advertising exchange platform, AdX.

On Monday, September 22, a lawsuit brought by the U.S. Department of Justice (DOJ) and a coalition of states against Google’s advertising business began trial in Alexandria, Virginia. Federal prosecutors are seeking to force Google’s parent company, Alphabet, to divest its global largest ad bidding platform, AdX, arguing that its monopolistic position harms online publishers who rely on the system for revenue.

Google’s AdX platform enables real-time programmatic advertising auctions between advertisers and publishers, connecting Demand-Side Platforms (DSPs) with Supply-Side Platforms (SSPs) through automated technology to facilitate efficient, targeted ad transactions. In this process, Google charges online publishers a 20% fee.

This case — threatening tens of billions in revenue — was first filed in 2023 and has now entered its second phase. In the first phase concluded in April, Judge Leonie Brinkema ruled that Google engaged in willful monopolization of the digital advertising market.

The DOJ argues that AdX’s dominant position has suppressed competition and innovation for years, and only structural change can restore a level playing field. Of all remedies, divestiture is the most effective and fastest solution.

Google, however, calls the proposed breakup “radical and reckless,” insisting it has already made sufficient changes and that viable, effective, and enforceable remedies remain possible within the next year.

According to eMarketer, Google leads the global digital ad market, valued at over $750 billion. The company is projected to generate $86.3 billion in digital ad revenue in the U.S. this year, with $15.9 billion directly tied to the current antitrust case.

This lawsuit is one of three major antitrust cases the U.S. government has brought against Google. Earlier this month, Google won a key victory when a court rejected the DOJ’s demand to sell Chrome, and the company is also appealing a separate case related to opening up its app store.

Given Google’s performance in the search engine case — where the court ruling was widely seen as a symbolic, light penalty that avoided forced divestiture — capital markets have reacted relatively calmly to this latest ad monopoly case.

Google’s stock has risen 21% this month, hitting a new record high and making it the fourth company ever to surpass a $3 trillion market cap. On Monday, shares dipped less than 1%, closing at $252.88.

Google’s legal team argued that AI-driven technologies from competitors like Meta are already reshaping how the ad market operates — rendering the DOJ’s drastic proposal unnecessary.