Technology giant Google has been fined €220m (£189m) by French authorities for abusing its advertising power.
France's competition watchdog said Google has been promoting its own online advertising services to the detriment of rivals.
It found that Google's ad management platform for large publishers, Google Ad Manager, favoured the company's own online ad marketplace, Google AdX.
Google said it would make changes to its advertising business.
The US tech giant has agreed to make it easier for publishers to use its data and tools. "We will be testing and developing these changes over the coming months before rolling them out more broadly, including some globally," the company said.
It is not the first time the company, owned by Alphabet, has been slapped with heavy fines for falling foul of European advertising rules.
Google was fined €1.49bn (£1.28bn) by the EU for blocking rival online search advertisers in 2019.
It was also fined €50m (£44m) in 2019 by the French data regulator CNIL, for a breach of the EU's data protection rules.
The EU competition authority fined the company a record €4.34bn (£3.9bn) fine in 2018 for using its popular Android mobile operating system to block rivals.
That followed a €2.42bn fine in 2017 for hindering rivals of shopping comparison websites.
"The decision to sanction Google is of particular significance because it's the first decision in the world focusing on the complex algorithmic auction processes on which the online ad business relies," said Isabelle de Silva, chief of France's Autorité de la concurrence (Competition Authority).
The watchdog said Google Ad Manager provided AdX with strategic data such as the winning bidding prices, while AdX also enjoyed privileged access to requests made by advertisers via Google's ad services.
Meanwhile, AdX exchanged data more smoothly with Ad Manager than with other advertising management platforms. The platforms are crucial for publishers to manage and sell advertising space.
French Finance Minister Bruno Le Maire said: "The practices put in place by Google to favour its own advertising technologies have affected press groups, whose business model is heavily dependent on ad revenues. These are serious practices and they have been rightly sanctioned."
The French authority launched its investigation in 2019 following a joint complaint from News Corp, French news publishing group Le Figaro and Belgian press group Rossel.
It said its decision opens the way for publishers who felt disadvantaged to seek damages from Google.
"While we believe we offer valuable services and compete on the merits, we are committed to working proactively with regulators everywhere to make improvements to our products," said Maria Gomri, legal director, Google France.