It's a popular messaging app for millions of people around the world, but WhatsApp will no longer work on some smartphones from February 1.
Android and iPhone devices which only support outdated operating systems will no longer be able to run the Facebook-owned app.
WhatsApp said the move would protect the security of its users.
Smartphones using Android 2.3.7 and older, and iPhone iOS 8 or older, are those affected by the update.
Thankfully, most smartphones are compatible with more up-to-date operating systems, so you should be able to update your device.
For example, iOS 9 is available for iPhones going back as far as the iPhone 4s.
To find out which operating system your iPhone uses, go to Settings, then General, then Software Update - your current version will be displayed there.
Meanwhile, on Android, you can find out your operating system, by going to Settings, then About Phone, then Software Info.
