Older Android and iPhone devices will no longer support the latest version of the app, forcing owners to either update their mobile operating system or buy a new smartphone.
Any iPhone not running iOS 9 or newer, or any phone not running at least Android 4.0.3 – also known as Ice Cream Sandwich – will no longer be able to open or operate the Facebook-owned app.
This means all iPhone models up to the iPhone 4 will be unable to support WhatsApp, as these phones are not capable of updating to iOS 9.
The iPhone 4S, iPhone 5, iPhone 5S, iPhone 6 and iPhone 6S were all released before iOS 9, however owners can still update to the operating system if they are yet to do so.
Android phones that will lose WhatsApp support include the Samsung Galaxy S2, HTC Desire and LG Optimus Black.
Phone owners can see what software their device is using by checking the settings section. For iPhone users, this can be found under Settings > General > Software update.