European Union regulators have fined Google $A2.4 billion (1.49 billion euro) for abusing its power in online advertising and blocking ads.
It is not the first time the search engine giant has been slapped with an antitrust penalty.
Google has previously been fined billions by the commission from separate probes into two other parts of the business.
Margrethe Vestager, the EU’s competition commissioner, revealed the results of the probe of Google’s AdSense business at a news conference in Brussels on Wednesday.
She said: “Today’s decision is about how Google abused its dominance to stop websites using brokers other than the AdSense platform”.
The commission uncovered Google and its parent company, Alphabet, breached EU antitrust rules by forcing constrictive clauses in contracts with Adsense users’ websites, which prevented Google rivals from placing their ads on these sites.
According to Vestager, Google “prevented its rivals from having a chance to innovate and to compete in the market on their merits.
She added: “Advertisers and website owners, they had less choice and likely faced higher prices that would be passed on to consumers”.
AdSense is a Google product that lets websites add text ads on their websites, with the ads based off results from search functions on their sites.
Microsoft has previously filed an EU antitrust complaint about AdSense in 2009, with the EU Commission officially launching its probe in 2016.
Last year, Vestager hit Google with a record $A6.9 billion (4.3 billion euro) fine following an investigation into its Android operating system.
The year prior in 2017, she fined Google with a $A3.7 billion (2.42 billion euro) fine in a case involving its online shopping search results.