The US and Alphabet Inc.’s Google are facing off in a trial over claims the company engaged in anticompetitive practices — a key test of the government’s ability to limit the power of technology giants like Google, Amazon.com Inc., Apple Inc. and Meta Platforms Inc.

Government officials have sought to crack down on the four big tech companies, which have a combined market value of more than $6.6 trillion and provide services that shape how consumers live. Lawmakers allege the companies act as “gatekeepers” who use their structural advantages in the online economy to disadvantage competitors and stifle innovation.

The high-profile trial with Google, which began Tuesday in Washington, is the first courtroom clash between the federal government and an American tech company in more than two decades.

According to the US Justice Department, Google unlawfully wields monopoly power by paying $10 billion a year to rivals, smartphone manufacturers and wireless carriers to make its search engine the default option on mobile devices and web browsers. The company denies it thwarts competition. It argues there are other options, but users choose Google because it has the best search tool.

A loss in court for Google could undermine the company’s $96 billion business from ads on US web searches, according to Jennifer Rie, a Bloomberg Intelligence antitrust litigation analyst. The company faces a separate suit filed in January by the Justice Department and 17 states that accused the company of unlawfully monopolizing the digital ad market.

Google, Amazon, Apple and Meta have been targeted in more than a dozen US antitrust investigations or complaints challenging fundamental parts of their business models and, in some cases, seeking to unwind key acquisitions. Microsoft Corp. was sued by the Justice Department in the 1990s, and more recently succeeded in defending itself in a bid by the Federal Trade Commission to block the $69 billion acquisition of Activision Blizzard Inc.

Google’s practices also are under fire in Europe, where the company has been fined more than €8 billion ($8.6 billion) over complaints for anti-competitive practices. In June, the European Union fired off more charges, accusing Google of favoring its advertising technology business to the detriment of adtech rivals, advertisers and online publishers, and told it to divest the entire division.

Here’s a list of the active, appealed and settled antitrust cases facing Google, Amazon, Apple and Meta:

(Updates with details on trial, tentative settlement in Google Play litigation, big tech case dismissals.)

Author: Leah Nylen, Malathi Nayak and Brody Ford