Google was sued in the US by advertising exchange PubMatic, which is seeking billions of dollars over its claim that the search giant has illegally monopolised the ad technology market.

The lawsuit, filed in Virginia, is the second by an advertising exchange to take aim at the tech giant since a federal judge ruled in April that Google had illegally monopolised two key technology markets – ad exchanges and tools used by websites to sell ad space, known as ad servers.

The judge in Virginia, who sided with the justice department and a handful of states in April, has set another trial for this month to decide whether Google must sell off parts of its advertising business to remedy the illegal conduct.

PubMatic chief executive Rajeev Goel said the earlier ruling that Google has illegally maintained monopolies in advertising technology was “meaningful but not complete.” The company’s lawsuit isn’t just about money, but making sure online advertising markets work, he said.

“It felt like for many years no matter how well we innovated there was a barrier holding us back,” Goel said in an interview. “That barrier wasn’t the limits of our technology. It was Google’s illegal monopoly. Every time we adapted or innovated, Google found new ways to stack the deck.”

PubMatic helps websites, including Elon Musk’s X, sell advertising space. Google considered buying the company in 2011, according to documents and testimony from the antitrust trial last year, but instead purchased advertising technology provider AdMeld.

Last month, OpenX Technologies, another ad exchange, sued Google in the same Virgina court. The Alphabet unit also faces a case by another group of states led by Texas, as well as a raft of lawsuits from website publishers and advertisers seeking damages for the same conduct. The publisher and advertiser suits are pending in New York, and Google has sought to transfer OpenX’s case there, though the judge in the case hasn’t yet ruled on the request. – Blo – berg