WhatsApp back in service after outage cut millions off
The Facebook-owned instant messaging app, which has more than 1.2 billion users, began experiencing problems on Wednesday evening.
But by 11.20pm, many reported being able to access the service once again.
WhatsApp has not commented on the cause of the problem, but complaints posted on social media quickly made the service the top trend in the UK on Twitter.
Many users reported being able to open the app, but not able to connect to its servers, making it impossible to send or receive messages.
Web service monitoring site Down Detector reported that issues with the app started at around 9pm in the UK, with problems also reported in the US, South America and Asia.