Facebook crashed this afternoon, leaving millions of users without access to their personal data.
The site, which claims to have 1.23bn monthly users, displayed an error message to users who were trying to log on.
In a rare outage, visitors to the Facebook website just before 5pm UK time were greeted with a message reading "Sorry, something went wrong. We're working on getting this fixed as soon as we can."
And users of the network's mobile apps saw a network error.
Founder Mark Zuckerberg once gave advice to business founders by saying: "Move fast and break things. Unless you are breaking stuff, you are not moving fast enough