The European Commission said Google, a division of Alphabet, had prevented third parties using its AdSense advertising service from displaying search advertisements from Google's competitors.
Google was hit with a $1.7 billion (1.49-billion-euro) fine on Wednesday, the third antitrust sanction from the European Union in two years after a record-breaking $4.96 billion (4.34 billion euro) penalty last year and a $2.74 billion (2.4-billion-euro) sanction in 2017 over its anti-competitive practices.
The ruling comes at a time when big tech companies around the world are facing increasing regulatory pressure and fierce political attacks over privacy violations, online misinformation, hate speech and other abuses.
Still, the latest penalty isn't likely to have much effect on Google's business.
It involves practices the company says it already ended, and the sum is just a fraction of the $31 billion in profit that its parent, Alphabet, made last year.
Alphabet stock rose 2 percent on Wall Street on Wednesday.
The EU ruling applies to a narrow portion of Google's ad business: when Google sells ads next to Google search results on third-party websites.
Investigators found that Google inserted exclusivity clauses in its contracts that barred these websites from running similarly placed ads sold by Google's rivals.
As a result, advertisers and website owners "had less choice and likely faced higher prices that would be passed on to consumers," said the EU's competition commissioner, Margrethe Vestager.
Anyone who suffered from Google's behavior can seek compensation through national courts, she said.
Here is a timeline of Google's antitrust cases in Europe:
* March 20 2019 - EU antitrust enforcers slap a $1.7 billion (1.49 billion-euro) fine on Google because it hindered rivals in online search advertising for a decade.
* July 18 2018 - EU antitrust regulators hand down a record $4.96 billion (4.34 billion euro) fine to Google over its Android mobile operating system after a three-year-long investigation.
* June 27 2017 - EU fines Google $2.74 billion (2.4-billion-euro) for thwarting rivals of shopping comparison websites.
* July 14 2016 - EU sets out another charge against Google's shopping service. It also accuses the company of preventing third parties using its AdSense product from displaying search advertisements from Google's competitors - a third case against the company.
* April 20 April 2016 - EU sends a charge sheet to Google outlining the company's anti-competitive practices with regard to Android smartphone makers and apps makers.
* April 15 2015 - EU opens investigation into Google's Android smartphone operating system.
* April 15 2015 - EU charges Google with blocking competitors of its price comparison shopping service.
* Sept 2014 - Joaquin Almunia, European Competition Co mmissioner at that time, says he will not be able to wrap up the Google case before his mandate ends in October.
* May 2014 - Almunia says feedback from complainants will be crucial to determining whether he accepts Google's concessions.
* Feb 5 2014 - Google improves its concessions related to online search.
* 2013 - Lobbying group FairSearch files a complaint about Google's Android business practices to the European Commission.
* April 25 2013 - EU seeks feedback from rivals and users to Google's concessions.
* April 3 2013 - Google offers concession s related to online search and its AdSense advertising network to address EU competition concerns, without admitting wrongdoing.
* Nov 30 2010 - European Commission opens investigation into allegations that Google has abused its dominant position in online searches following 18 complaints.
* 2010 - Microsoft complains about Google's practices related to its AdSense advertising service.
* Nov 3 2009 - British price comparison site Foundem complains about Google's online search to the European Commission.