WhatsApp will no longer function on certain older smartphones that cannot upgrade to iOS 15.1 or higher beginning May 5, 2025. Users with these devices will be unable to send or receive messages on the app unless they switch to newer models.
This move is part of WhatsApp’s routine updates to maintain performance, security, and compatibility with the latest features. Devices that lack the ability to upgrade to the required operating system will be phased out of support.
After May, 5 only devices running the iOS 15.1 operating system or newer will be supported. Currently, WhatsApp supports iOS 12 and later, but with a future update, the app will require iOS 15.1 or newer to work properly.

The affected devices are the iPhone 5s, that was released in 2013, iPhone 6 and iPhone 6 Plus that was released in 2014.
One of the main reasons for this change is that newer versions of iOS include updated APIs and improved technologies that WhatsApp relies on to deliver new features.
By not supporting older versions, WhatsApp will be able to optimize the app and introduce new features that simply wouldn’t be possible with outdated operating systems.