Facebook owned messaging service WhatsApp will no longer work on millions of smartphones from February 1st 2020.
Android and iPhone devices that are only supported by outdated operating systems will no longer be able to run this app.
WhatsApp stated that the move was important, in order to protect the security of its users.
Smartphones using Android 2.3.7 and older, and iPhone iOS 8 or older, are the main users affected by the update.
The operating systems that WhatsApp will be providing support for are legacy operating systems, which are no longer updated or installed on new devices.
Most users will still be able to update their operating systems in order to continue using the messaging service.
However, certain devices, such as iPhone 4s, which only support iOS 7, will no longer be compatible with the What's App.
"WhatsApp clearly had no option but to ensure its service remains secure, however it faces the difficult side-effect that the app is no longer compatible with older smartphones," said CCS Insight analyst Ben Wood.
"This is likely to disproportionally impact the long-tail of its users, particularly in growth markets where there is a high proportion of older devices."