Elon Musk's social media company X breached EU online content rules, EU tech regulators ruled on Friday in a finding that could lead to a fine and significant changes in how it operates.

The move by the European Commission follows a seven-month-long investigation under the Digital Services Act (DSA), which requires very large online platforms and search engines to do more to tackle illegal content and risks to public security.

ByteDance's TikTok, AliExpress and Meta Platforms are also being investigated under the DSA.

The EU executive singled out X's dark patterns, advertising transparency and data access for researchers.

It said X's verified accounts, which carry a blue checkmark, do not correspond to industry practice and negatively affect users' ability to make free and informed decisions about the authenticity of the accounts they interact with.

X has also failed to comply with a DSA requirement that companies provide a searchable and reliable advertisement repository, the commission said.

X was also charged with blocking researchers from accessing its public data. The company, which will have several months to respond to the charges, could face a fine of as much as 6 percent of its global turnover if found guilty of breaching the DSA.

"X has now the right of defense – but if our view is confirmed we will impose fines and require significant changes," EU industry chief Thierry Breton said in a statement.

The commission said separate investigations continue into the dissemination of illegal content on X and the measures it has taken to counter disinformation.