The European Commission fined Google in 2018, saying that it had used Android since 2011 to thwart rivals and cement its dominance in general internet search.

Regardless of how the court rules, Google, Apple, Amazon and Facebook will have to change their business models in the coming years to ensure a level playing field for rivals following tough new rules proposed by European Union antitrust chief Margrethe Vestager.

"By defining markets too narrowly and downplaying the potent constraint imposed by the highly powerful Apple, the Commission has mistakenly found Google to be dominant in mobile operating systems and app stores, when it was in fact a vigorous market disrupter," he said.

Google and Apple pursue different models," he told the court.

Khan cited Google's agreements which forced phone manufacturers to pre-install Google Search, the Chrome browser and the Google Play app store on their Android devices, and payments to pre-install only Google Search as conduct that did not allow for competition.