Instagram, Facebook, Messenger and Threads suffered widespread problems on Tuesday afternoon, with users locked out of their accounts and pages failing to load properly.
Facebook outages reported on Down Detector shot up just before 3pm, with more than 300,000 problems logged.
More than 25,000 Instagram outages were also reported via the website, which collates status reports from several sources, including users.
Problems on Facebook left some users unable to login, while others were logged out and unable to reset their passwords or access their accounts.
Meanwhile, Instagram users struggled to load timelines, stories and comments.
The social media platforms were back up and running by 6pm, according to their parent company, Meta.
WhatsApp, which is also owned by Meta, appeared to be unaffected by the problems.
Sky News understands some of Meta’s internal systems were also affected by the outage. The company has been contacted for comment.
Andy Stone, communications director at Meta, posted on X when the problems were first reported: “We’re aware people are having trouble accessing our services. We are working on this now.”
He later added: “Earlier today, a technical issue caused people to have difficulty accessing some of our services.
“We resolved the issue as quickly as possible for everyone who was impacted, and we apologise for any inconvenience.”
London-based internet monitoring firm Netblocks said on X that the four Meta platforms experienced the login issues in “multiple countries”.
But the firm, which advocates for internet freedom, said there was no sign of “country-level internet disruptions or filtering,” which are typically imposed by governments.