WhatsApp users could find themselves no longer able to use the app after the clock strikes midnight, when the technology stops running on older phones.
Changes in technology will see the hugely popular app stop working on certain mobiles, meaning that some users will be forced to upgrade their handsets if they want to continue using the service.
The popular messaging app, which has more than a billion users worldwide, announced earlier this month that it will no longer support a range of older operating platforms by the end of the year.
The changes are expected to affect millions of users globally, who use handsets including the iPhone 3GS and Windows Phone 7.
WhatsApp said it will be phasing out support for older Windows, Android and Apple models by January, with the service set to end for Blackberry users and Nokia models by mid-2017.
The older smartphone platforms can no longer keep up with the latest features being rolled out for the app, claims a blog post by the Facebook-owned app.
WhatsApp made the announcement as it celebrated its seventh anniversary, after first launching the popular messaging platform in 2009.
The app, which is now used by more than one billion people worldwide, was launched in the early days of Apple’s App Store, when seven out of ten had operating systems offered by Blackberry and Nokia.
However, today’s smartphone market is dominated by Google, Apple and Microsoft, with almost all newer models running on these platforms.
The firm wrote: ‘As we look ahead to our next seven years, we want to focus our efforts on the mobile platforms the vast majority of people use.’
The full list of platforms being left behind at the end of the year includes: Android 2.1 and Android 2.2; Windows Phone 7 and iPhone 3GS/iOS 6.
And by June 2017, WhatApp will no longer be available for BlackBerry, including BlackBerry 10; Nokia S40; and Nokia Symbian S60.
WhatsApp explained: ‘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.’
Users still on one of the listed platforms are advised to upgrade to newer Android, iPhone or Windows phone platforms.
The firm added: ‘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.’
In its seven years since being set up by former Yahoo! employees Jan Koum and Brian Acton in Canada, the messaging app has grown from strength to strength.
Last month, WhatsApp officially launched video calling, in a bid to compete with Apple’s Facetime and Skype.
In keeping with WhatsApp’s data security standards, the new video calling feature will be fully encrypted, protecting calls from being listened into.
The move comes as privacy advocates worry about the potential for stepped-up government surveillance in the US under a Trump administration.
WhatsApp, which boasts more than a billion users worldwide, adopted end-to-end encryption early this year, making it technically impossible for the company or government authorities to read messages or listen to calls.