The latest fine is almost double the previous one of 2.4 billion euros, which was also against Google in 2017 in the online shopping comparison case.
"Today, mobile internet makes up more than half of global internet traffic", Ms Vestager added.
Commissioner Margrethe Vestager, in charge of competition policy, said the case focused on three types of restrictions that Google imposed on Android device manufacturers and operators. Denying rivals a chance to innovate and compete on the merits.
Google says Android, which is free for manufacturers to use, has increased competition among smartphone makers, lowering the prices for consumers.
Although Google's appeal is likely to begin a game of table tennis between itself and the European Commission that will last years, this concludes the lengthy investigation into the Android operating system. It's the highest anti-competition penalty ever imposed on a company by the EU.
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That would pave the way for the entire city to come under government control in accordance with the handover deal. A group affiliated with the Islamic State group holds a sliver of territory on the southern tip of the region.
The sanction almost doubles the previous record European Union anti-trust fine of 2.4 billion euros, which also targeted Google, in last year's case for the Silicon Valley titan's shopping comparison service.
Under EU rules, Google could have been fined up to 10 percent of parent company Alphabet Inc's annual revenue, which hit US$110.9 billion previous year.
Android is the operating system that runs on 85.9pc of smartphones in the world today, according to Gartner. That would mean Android device makers would no longer need to pre-install Google Search and Chrome in Android. That gives Google too much power over competition between different operating systems, the European Union says.
The EC isn't done examining Google's business practices, saying that it "continues to investigate restrictions that Google has placed on the ability of certain third-party websites to display search advertisements from Google's competitors". Android manufacturers who wanted to pre-install Google's apps couldn't use Amazon's Android fork, for instance, and could only use Google's version of Android.
Google has been ordered to stop the practices within 90 days, or face additional penalties.
Google's search business would not be significantly harmed even if Android users did switch to iOS, because Google also has deals with Apple to implement Google search on iOS. "In competitive mobile markets, consumers should be able to make a meaningful choice between search engines and browsers and which apps they can download on their phones and tablets". But Brussels has had USA tech giants in its sights for a decade in a half, since it imposed a huge 497 million euro fine on Microsoft in 2004 for anti-competitive behaviour and ruled it must make changes to its Windows system. The existence of a varied app store allows users to replace any pre-loaded application with an alternative quickly.