In regards to the other two major operating systems, WhatsApp specifies that Android smartphones running on versions 2.3.7 and older will have until 1 February 2020. The same deadline is also applicable for iPhones still on iOS 8 or older as well. After the date, phones still running on said OS versions will be unable to create new account or re-verify currently existing accounts. On another note, WhatsApp also mentioned that it will still provide support for devices running on Android OS 4.0.3 and iPhones running on iOS version 9 and later. Also, WhatsApp will also continue providing support to users who happen to be using a smartphone powered by Firefox-based KaiOS 2.5.1 or later.
The decision to end support for Windows Phone OS isn’t all that surprising, in particular. First introduced back in 2010 as Windows Phone 7, the mobile operating was an effort for Microsoft to stay relevant in a mobile OS ecosystem that is currently dominated by Google’s Android and Apple’s iOS. In 2015, Microsoft officially discontinued development of the OS. (Source: WhatsApp via Techspot, CNET)