WhatsApp is dropping support for some older phones, including all BlackBerry models.
The Facebook-owned messaging service will also no longer support some Nokia and Android devices by the end of the year.
WhatsApp says that using developer time on these devices could hold back the app’s growth.
In a blog post the company said: “When we started WhatsApp in 2009, people’s use of mobile devices looked very different from today.
“The Apple App Store was only a few months old. About 70% of smartphones sold at the time had operating systems offered by BlackBerry and Nokia.”
These days, BlackBerry has less than 1% market share as Apple and Samsung dominate worldwide phone sales.
Every BlackBerry, including ones running the relatively new BlackBerry 10, will be hit, along with the Nokia S40, Symbian S60 and any phone running Android 2.1 and 2.2, plus Windows Phone 7.1.
WhatsApp advised those with the affected phones to upgrade to newer models.
The blog post 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.”