“Because we no longer actively develop for these operating systems, some features might stop functioning at any time,” a WhatsApp blog post explained.
“For the best experience, we recommend you use the latest version of iOS [or Android] available for your phone.”
12 useful WhatsApp features you didn’t know existed
Show all 12
The latest update will mean users on unsupported devices will no longer be able to create new accounts or reverify existing accounts.
Apple devices affected include any iPhone running iOS 8 or earlier, meaning anyone with an iPhone 4 or older will no longer be able to use WhatsApp.
Certain other phones that were released before iOS 9 was launched will be able to update to the newer operating system. These include the iPhone 4s, all models of the iPhone 5 range and all models of the iPhone 6 range.
The range of Android devices that will continue to be supported is a lot broader, with any phone released after 2011 safe from being cut off.
Any smartphones running Android 2.3.7 – also referred to as Gingerbread – will be hit, as well as all older versions of the OS.
“While these mobile devices have been an important part of our story, they don’t offer the kind of capabilities we need to expand our app’s features in the future,” WhatsApp said.
"This was a tough decision for us to make, but the right one in order to give people better ways to keep in touch with friends, family, and loved ones using WhatsApp.
Join our commenting forum
Join thought-provoking conversations, follow other Independent readers and see their replies