Facebook and Instagram users are desperate to know when the social media platform will come online.
The two apps - along with Messenger and WhatsApp - suddenly stopped working on Monday evening.
As of 6.10pm, the reason for the outage has yet to be revealed by Facebook - which has more than 51.1 million users in the UK alone.
But when will Facebook be back up and running again?
The company, which was first founded in 2004, has not yet specified a time.
However, the firm's communications executive Andy Stone said it was "working to get things back to normal as quickly as possible" and it apologised "for any inconvenience".
A similar message was also posted by WhatsApp, which is owned by Facebook.
Last time a problem of this scale happened, in March 2019, it took 24 hours before everything went back to normal.
Have Facebook had any other problems recently?
Earlier this year it was revealed that the stolen data of 533 milllion Facebook users were leaked online.
The exposed data included the personal information ofFacebook users from 106 countries, including over 32 million records on users in the USA, 11 million on users in the UK, and 6 million on users in India. It includes their phone numbers, Facebook IDs, full names, locations, birthdates, bios, and, in some cases, email addresses.
Facebook said in reply: "We understand people's concerns, which is why we continue to strengthen our systems to make scraping from Facebook without our permission more difficult and go after the people behind it."
