WhatsApp has ended support for iOS 9 and earlier versions, which means the app will no longer work on the iPhone 4s.
A support document notes that WhatsApp now requires all users to be running at least iOS 10, which launched in 2016. This means that iOS users will need an iPhone 5 or later model to use the Facebook-owned messaging app.
The change comes with version 2.21.50 of WhatsApp for iPhone, which is now available to download from the App Store.
Here are the new requirements for the app:
Users who are using WhatsApp on an unsupported device are encouraged to export their chat history before losing access to the app.