Facebook users have reported that the website is down for social networks.
People went to Twitter with the hashtag #facebookdown.
At this point it is not known what caused the failure.
Instagram, which is owned by Facebook, will stop working for users in a similar outage – the users’ feeds will not be updated.
People have said they thought their wifi was down until they checked Twitter and saw the trending hashtags.
The independent failure monitor Down Detector has seen a huge surge in Facebook down reports, with tens of thousands of reported issues.
According to Down Detector statistics, more than two thirds of the affected Facebook users were affected by a total failure, while around a quarter were affected by login problems.
Facebook users have also reported receiving an error code 1 message.