WhatsApp has gone down for users across the world in a 'global outage'.
Downdetector.co.uk recorded more than 68,000 reports about the messaging app between 8.45pm and 9.15pm.
The platform now appears to be working again for most people, with the number of reports on Down Detector decreasing from around 9.30pm.
Mobile and web customers said the app was not 'connecting' when they try to send messages.
Some 88% of the problems reported on Down Detector were connection-related.
The spike in reports took place shortly after 8.30pm.
Users have been affected all over the world, including vast swathes of Europe, the US, southern and central America, India and Australia.
WhatsApp is now trending on Twitter, with more than 321,000 tweets about the outage.
Twitter users have shared funny memes expressing their shock at the issues, alongside the hashtag #whatsappdown.
The service also went down last month, when thousands of users reported problems.
According to independent monitor Down Detector, a huge spike of in complaints was recorded shortly before 5pm.
The majority of these were around the last seen feature, while 24% said they were having connection problems.
Users said they could not see when their contacts were last online, and were unable to adjust their security settings.
A map on the Down Detector website said that issues were being reported around the world, but with Europe appearing to be the epicentre.
