Elon Musk's X platform went down for tens of thousands of global users, including thousands in the UK.
According to outage tracking website Downdetector.com there were problems for as many as 79,000 users in the US alone on Friday.
Users in the UK reported more than 13,600 issues with X, formerly known as Twitter, at 3.24pm, and more than 10,200 reports were received at 3.54pm, the website shows.
But the platform for now appears to be working again for many users.
More than 3,000 issues were reported in India.
Issues were also reported in Australia, with more than 2,700 users reporting problems.
Users reported being unable to load their feed or reply to direct messages and repeatedly shown the message: "Something went wrong. Try reloading".
"Unable to reply to chat messages as keeps showing disconnected, feed not updating," one user told Downdetector.
"Can't load posts," another said.
Another user said: "Had problems several days ago and now it's not loading 'My Messages', 'Following' or 'For You'."
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The actual number of users affected by the X outage could be greater as the figures are based on reports by users.
In November, a Cloudflare outage briefly prevented access to X after a faulty security configuration crashed its traffic system.
A few days later, another disruption took X offline for thousands of American users.
The outage comes just days after the social media platform implemented changes to its AI tool Grok to prevent users from undressing pictures of real people.
The move followed widespread criticism of the tool for sharing non-consensual sexual images through image editing.
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