Google's inability to roll out updates to all Android smartphone users at once is one of the biggest problems of the platform, leading to fragmentation across the market. These practices have denied rivals the chance to innovate and compete on the merits.
"Prevented manufacturers wishing to pre-install Google apps from selling even a single smart mobile device running on alternative versions of Android that were not approved by Google (so-called "Android forks")".
According to the European Union commission, Google is also obliged to end its illegal activities within ninety days after the commission has made the decision.
This amount is nearly double that of a previous fine of $2.7 billion the company received in 2017 for unfairly favoring its own services in internet search results.
Much of the attraction of today's smartphones lies in the apps users can download and install on them, and Google Play offers by far the largest range of apps of any app store for mobile phones.
Past year eMarketer forecast almost $50billion would be made by Google in 2017 from mobile ad revenue.
Google's parent company Alphabet said in a regulatory filing it would accrue the fine in the second quarter of 2018.
Trump has lashed out at the EU - defending Google and saying he was right over European agendas.
"Android has created more choice for everyone, not less", it said in a statement.
Polar Capital fund manager Ben Rogoff said: "The reality is that as long as they're delivering great utility to their consumers, consumers will still use those platforms", he said.
"Plaintiffs that were not sure whether they have a case will now feel emboldened and may be more confident to challenge Google", said Nicolas Petit, a professor at the University of Liege and visiting fellow at Stanford's Hoover Institution.
"There is a significant danger of unintended consequences that penalizes the consumer". The fine marked the second time in about a year that regional regulators have needled Google for its business practices.
The U.S. has also complained that the European Union has mainly targeted American companies - including also Apple and Amazon - for breaking competition or tax rules.
Danish former minister Vestager spoke by telephone with Google chief Sundar Pichai on Tuesday night to tell him about the decision in advance. Facebook will also be looking for changing its business model under pressure.
"Separating Google's search engine from its commercial activities is necessary to restore level playing field", said Ramon Tremosa, a member of the European Parliament.