EU antitrust regulators plan to open an investigation into the technology industry, according to a European Commission document seen by Reuters, a sign of more regulatory problems ahead for Google, Facebook, Amazon and other online groups.
As many as seven billion daily searches make the US giant "the front page of the internet", Nicholas Khan, a lawyer for the European Commission told a panel of judges in the opening session of a three-day hearing at the EU General Court in Luxembourg.
The first significant fine against Google was levied in 2017, when the European Commission fined it 2.4bn euros (£2.01bn) after it ruled that Google had thwarted rivals of shopping comparison websites.
The EU has fined Google a total of 8.25 billion euros in three separate cases, including one involving its Android smartphone operating system and Google's favouring its own price comparison shopping service to the disadvantage of smaller European rivals.
In the meantime, Margrethe Vestager in her new beefed-up role as Europe's digital chief will not be idle.
The appeal hearing is set to run for three days.
Google is expected to plead that the commission has wrongly applied arguments used successfully against Microsoft and that the company has the right to give advantage to its own services. For example, in November 2019, Google Shopping's rivals claimed the penalty hadn't incentivized the company to change its anti-competitive behaviour.
The commission was joined by other plaintiffs, who shot down Google for aggressive business practices.
"Our traffic decreased considerably, which created a vicious circle with merchants who no longer saw us as an alternative to Google Shopping", said Laurent Godfroid, a lawyer for Twenga, a rival to Google Shopping.
It also represented the biggest regulatory setback yet for Google.
More than 30 travel firms - including TripAdvisor and Expedia - wrote to Vestager on Monday complaining that Google was unfairly trying to enter the vacation rental ad business.
That was "unjustified", Google said, according to the report, arguing that it "cooperated constructively" with the European Union and "did not hide the practice at issue which rules out the need for a specific deterrence component".
The EU has already said it was looking into Google's similar push into job ads.