WhatsApp to end support for Windows Phone, older Android and iOS versions
In case you're wondering why WhatsApp has decided to turn off support for Windows Phone ahead of 2020, it's worth mentioning that this is consistent with Microsoft's decision to end support for their mobile operating system.
Concerning the other two operating systems, WhatsApp will stop working on devices running Android version 2.3.7 and older starting February 1, 2020. Also, devices powered by iOS 7 and older will no longer be compatible with WhatsApp effective February 1, 2020.
However, since WhatsApp won't be developing for these operating systems anymore, some features that are now available might stop working even before the deadline, so you might want to switch to a newer device if you want to continue to use WhatsApp.
Moreover, if you're using a device that runs these older Android and iOS versions, you won't be able to create new accounts, nor reverify existing accounts, as of right now.