Millions of Blackberry, Nokia and some Android and Windows users will see WhatsApp stop functioning on their phones as the social networking app ceases OS support on some models.
While celebrating its seventh anniversary, WhatsApp announced that it will stop supporting its messaging service on all BlackBerry OS versions including the latest BlackBerry 10.
The company also said that by the end of 2016 it will end support on the Nokia S40, Nokia Symbian S60, Android 2.1, Android 2.2, and Windows Phone 7.1.
In a blog post, the company said: "Anniversary dates are also an opportunity to look back. About 70% of smartphones sold at the time  had operating systems offered by BlackBerry and Nokia.
"Mobile operating systems offered by Google, Apple and Microsoft – which account for 99.5% of sales today – were on less than 25 percent of mobile devices sold at the time.
"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."
WhatsApp said that the mentioned devices do not offer the necessary capabilities for the company to expand its app’s features in the future.
The post also 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.
"If you use one of these affected mobile devices, we recommend upgrading to a newer Android, iPhone, or Windows Phone before the end of 2016 to continue using WhatsApp."
BlackBerry has been losing market share in the smartphone space, according to Gartner’s 4Q 2015 global smartphone sales.
BlackBerry’s OS market share in the last quarter of 2015 decreased from 0.4% in 4Q 2014 to 0.2% with 887,000 units sold. In comparison, Android OS dominates with 80.7% of the market share, followed by Apple’s iOS with 17.7% and Windows with 1.1%.