Facebook, WhatsApp and Instagram are all working again after they crashed for several hours.
A “faulty configuration change” was blamed for the shutdown that hit billions of people around the world.
The crash cost Facebook – which owns all the platforms – more than £36 billion off its value.
Founder Mark Zuckerberg is reported to have lost £4 billion.
Facebook Engineering said in a statement on Twitter:
“To the huge community of people and businesses around the world who depend on us: we’re sorry.
“We’ve been working hard to restore access to our apps and services and are happy to report they are coming back online now.
“Thank you for bearing with us.”
Mike Schroepfer, Facebook’s chief technology officer, said on Twitter:
“*Sincere* apologies to everyone impacted by outages of Facebook powered services right now.
“We are experiencing networking issues and teams are working as fast as possible to debug and restore as fast as possible.”
“Our engineering teams have learned that configuration changes on the backbone routers that co-ordinate network traffic between our data centres caused issues that interrupted this communication.
“This disruption to network traffic had a cascading effect on the way our data centres communicate, bringing our services to a halt.
“Our services are now back online and we’re actively working to fully return them to regular operations.
“We want to make clear at this time we believe the root cause of this outage was a faulty configuration change.”
It’s estimated 2.8 billion people use the Facebook platforms – just under every other person in the world.