Social networking services Facebook, WhatsApp and Instagram have been restored after a six-hour shutdown, Facebook said.
The company says the reason was a failed system change.
All three services are owned by Facebook and could not be found on the web or in mobile apps.
Downdetector, which monitors the breakdown of social networking services, said it was the biggest error ever to occur, with 10.6 million reports of problems from customers around the world.
Services were cut off at 16:00 GMT and users started accessing the services around 22:00 GMT.
In a statement Tuesday, Facebook said that the poor configuration changes affected tools and systems within the company that were difficult to try to solve the problem.
It added that there is no "evidence that user data has been compromised as a result of this service outage".
On Monday, Facebook sent a message of apology to those affected by the shutdown of its services.
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.
— Facebook (@Facebook) October 4, 2021
Some people also reported problems using other Facebook-based services like Oculus, and apps that require Facebook login were affected, including Pokémon Go.
Prolonged breakdown of this level is rare. The turmoil in 2019 left Facebook and other apps out of reach for the world for more than 14 hours.
Several other tech companies, including Reddit and Twitter, laughed at facebook for the problems - prompting responses from affected apps.
👋 hello!
— WhatsApp (@WhatsApp) October 4, 2021
The harassment comes a day after an interview with a former Facebook employee who leaked documents about the company.
Frances Haugen told CBS news agency Sunday that the company had prioritized "growth over security".
On Tuesday he will testify before a Senate subcommittee in a session called "Protecting Children Online", on the company's research on the impact of Instagram on the mental health of young users.
The breakdown of social networking services is not uncommon. One week ago the Slack network services were temporarily suspended.
What makes this so popular is the scale and context.
Errors that involve the domain name system are resolved quickly. They are also often localized, and some people may not be able to open a website that can be viewed in other countries.
This disconnection, however, was global, and affected all of Facebook's many channels.
The length of time that the service was lost is also unusual. There were reports of "violence" at Facebook headquarters, when technicians made every effort to fix the problem.
The week had already gotten off to a bad start for Facebook- after a revealer in the so-called "Facebook Files" introduced himself on Sunday.
But the week has now gotten worse for that social network.
