Meta says it has resolved a "technical issue" which caused Facebook, Messenger and Instagram to go down.
Hundreds of thousands of users worldwide were unable to access them for around two hours on Tuesday.
People trying to log onto the websites and apps were finding error messages and were unable to refresh their feeds as normal.
Meta also apologised to those who had been affected, saying it resolved the problem as quickly as it could.
Tracking website Downdetector indicated the outages had affected multiple countries.
Meta's platforms are some of the most popular in the world. Facebook has three billion active monthly users, while Instagram is expected to hit 1.4 billion worldwide later this year.
Threads, its rival to Twitter, that was launched in 2023, also reported outages. WhatsApp - which Meta also owns - was unaffected.
The biggest outage Meta experienced was in 2021, when founder Mark Zuckerberg apologised for the disruption caused.
On that occasion Facebook, Messenger, Whatsapp and Instagram services went down for almost six hours.
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