WhatsApp will stop working on millions of smartphones from today, February 1.
The popular messaging service will no longer be supported by the outdated operating systems of several iPhone and Android smartphones.
WhatsApp have stated that the change was a necessary one in order to protect the security of the Facebook-owned app's users.
Smartphones using Android 2.3.7 and iPhones with iOS 8 or older will be affected by the update.
A spokesperson for the company 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.
It's understood that most users should be able to continue using WhatsApp by simply updating their phone's operating system, which ought to support the WhatsApp update.
iPhone users can find out which operating system they are on by going to Settings, then General and then Software Update.
Android users can find out which operating system they are on by going to Settings, then About Phone and then Software Update.
The latest update comes shortly after the 2019 news that WhatsApp would no longer be supported on Windows smartphones.