WhatsApp went down for about four hours on Thursday evening with the messaging app not working for people across the UK.
According to Down Detector website, WhatsApp started experiencing problems at 7pm on Thursday.
Some users reported the app was down and some said they had issues with their server connection and sending messages.
It's not immediately clear what caused the issue.
The company tweeted that services were running again at about 10.45pm.
And we're back. Happy chatting!
— WhatsApp (@WhatsApp)
Having originally tweeted that workers were "working to get things running smoothly again", a follow-up post at 10.45pm said "And we're back! Happy Chatting!"
WhatsApp is currently the top trend on Twitter with thousands of people tweeting about the outage.