WhatsApp has been hit by a major outage, stopping millions of people from using it around the world.

People couldn't send or receive messages using the Facebook-owned app, apparently because of a server problem. Service appears now to be gradually being restored.

The app didn't initially look broken, with chats and contacts able to load. But once a user was into a chat, the app just showed a "connecting" message that never resolves itself, and so new messages couldn't be sent or received.

12 useful WhatsApp features you didn’t know existed Show all 12 1 /12 12 useful WhatsApp features you didn’t know existed 12 useful WhatsApp features you didn’t know existed Unsend messages You can unsend a message by tapping and holding it, hitting the Delete symbol and selecting Delete for Everyone. The feature works for all types of messages, but only if they were sent less than seven minutes ago. 12 useful WhatsApp features you didn’t know existed Dodge the blue ticks WhatsApp’s blue ticks show when sent messages have been read, but you can disable them buy going to Settings > Account > Privacy > Read Receipts. However, bear in mind that, by doing so, you’ll lose the ability to see when your own sent messages have been read. Another, more fiddly way of reading your messages without triggering the blue ticks, is enabling Aeroplane Mode before opening your messages - just remember to close the app before switching Aeroplane Mode off again. 12 useful WhatsApp features you didn’t know existed Hide your 'last seen' time Prevent your friends from finding out when you were last online by hiding your last seen time. Go to Settings > Account > Privacy > Last Seen. As is the case with disabling read receipts, hiding your ‘last seen’ time will also stop you from seeing anybody else’s. 12 useful WhatsApp features you didn’t know existed Limit data usage You can control how much data you munch through on WhatsApp by limiting the types of media you automatically download on a mobile connection. Go to Settings > Data Usage and choose the best option for you. 12 useful WhatsApp features you didn’t know existed Customise notifications If you’re expecting an important WhatsApp message from someone, set a custom notification for them by opening the chat, tapping their name at the top and hitting Custom Notifications. 12 useful WhatsApp features you didn’t know existed Format your messages To jazz up any of your messages, simply highlight it by tapping and holding it, hit the More Options key on the pop-up menu and tap the formatting option you want - bold, italic, strikethrough or monospace. 12 useful WhatsApp features you didn’t know existed Type hands-free You can get Siri or Google Assistant to type your WhatsApp messages out for you by saying either “Hey Siri” or “Okay Google”, followed by the name of the person you want to message and the actual contents of the message. 12 useful WhatsApp features you didn’t know existed Mark chats as unread When you’ve read a message but can’t reply to it straight away, you can set a visual reminder by marking it as unread. On Android, long-press the conversation, and on iOS, swipe from left to right on a chat. 12 useful WhatsApp features you didn’t know existed Email entire conversations You almost certainly won’t do this on a regular basis, but it’s a handy option to have. You can export entire conversations - complete with emoji and media attachments - by hitting More inside a chat a selecting Email Chat. 12 useful WhatsApp features you didn’t know existed Mass-message contacts You can send the same message to lots of your contacts without lumping them all into one group, much like the BCC option on email, by hitting the New Broadcast option on the app’s main menu. 12 useful WhatsApp features you didn’t know existed Pin conversations You pin up to three contacts and groups to the top of your WhatsApp conversation list by tapping and holding a chat, then hitting the pin icon. 12 useful WhatsApp features you didn’t know existed Make things easier to find You can easily mark key messages with a star, allowing you to find them easily when you need to. Just tap and hold a message and hit the star icon to save it, and return to it later by selecting Starred Messages in WhatsApp’s main menu.

That also meant there was no easy fix to the problem, since it appears to be on WhatsApp's side. Shutting and opening the app, for instance, just reset the connecting message but wouldn't stop it showing.

The website Down Detector showed a huge spike in problems with the app, suggesting that almost everyone is unable to get online. The problems are focused in western Europe and Asia, but were reported across the world.

There were relatively few reports of problems from the Americas, but that might simply be a result of the fact that timezones mean that many people there were asleep.

WhatsApp Web, which uses the phone's connection, was also broken.

WhatsApp 'Delete for Everyone' feature lets you unsend messages

Unlike its owner Facebook, and many other large social networks and internet companies, WhatsApp doesn't maintain a page to give users information when the site is down. It has an official Twitter account that is supposed to post when it is experiencing problems – but that appears to have fallen into disuse, and hasn't posted since 2014.