A landmark antitrust lawsuit against Google begins today, with the California-based company accused of using illegal means to keep its monopoly power.

The historic legal battle against federal government lawyers – which comes just a week after Google’s 25th birthday – is set to be the biggest in almost two decades, the outcome of which could have repercussions for the rest of the tech industry.

The last comparable antitrust lawsuit was filed against Microsoft in 1998.

“Back then, Google claimed Microsoft’s practices were anti-competitive, and yet, now, Google deploys the same playbook to sustain its own monopolies,” the US Department of Justice claims in its lawsuit.

It is alleged Google protects its franchise by shelling out billions of dollars annually to be the default search engine on the iPhone and on web browsers such as Apple‘s Safari and Mozilla’s Firefox.

Google is also accused of rigging the market in its favour by requiring its search engine to be bundled with its Android software for smartphones if the device manufacturers want full access to the Android app store.

Google has denied any wrongdoing and claims it faces a wide range of competition despite commanding about 90% of the internet search market.

It argues its rivals range from search engines such as Microsoft’s Bing to websites like Amazon and Yelp, where consumers can post questions about what to buy or where to go.

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Top executives at Google and its corporate parent Alphabet Inc, as well as those from other powerful technology companies, are expected to give evidence during the court case.

Among them is likely to be Alphabet chief Sundar Pichai.

Court documents also suggest that Eddy Cue, a high-ranking Apple executive, might be called as a witness.

The lawsuit was brought by former president Donald Trump’s justice department, and President Joe Biden’s administration has pressed on with it.

US District Judge Amit Mehta is not expected to issue a ruling until early next year.

If he decides Google broke the law, another trial will decide what steps should be taken to rein in one of the tech world’s most powerful companies.