What is the service and how does it work?
Following on from the attack in Manchester last night, which left 22 people dead, Facebook launched its 'Safety Check' feature.
This allows users in the area of Manchester to check in, informing friends and family they are safe. If you are outside of Manchester and want to know if your friends are safe, simply search for 'Manchester' in the toolbar.
This is only the second time the feature has been activated in the UK. It was first enabled in the country following the Westminister attack in March.
It was first introduced in 2011 and had been used for natural disasters only until the 2015 attacks in Paris. It has since been used following attacks in Berlin and Nice.
People of Manchester have been using Twitter to offer accommodation and food to those in need since the attack took place last night. #RoomsForManchester, #Manchester and #MissingInManchester have been trending over the past number of hours.
The Greater Manchester Police force have been using Twitter to keep members of the public informed.