Facebook-owned WhatsApp will not work on some iPhones and Android phones with dated operating systems from January 1, 2021. WhatsApp will only support android phones running on the Android 4.0.3 operating system or newer versions and iPhones running on iOS 9 and newer versions, according to the WhatsApp FAQ section. 

Here is the list of iPhones that will not support WhatsApp 

From next year, WhatsApp will not function on all iPhone 4 and earlier models including the iPhone 4S, the iPhone 5, the iPhone 5S, the iPhone 6, and the iPhone 6S. 

To continue using WhatsApp, you will have to update iPhone 4S, iPhone 5, iPhone 5S, iPhone 5C, iPhone 6, and iPhone 6S to iOS 9 or later versions.  

If you have iPhone 6S, 6 Plus, and iPhone SE first generation, you have to update it to the latest version of the system, iOS 14. 

The list of Android phones that will not support WhatsApp 

Similarly, several Android phones will lose WhatsApp support including the Samsung Galaxy S2, HTC Desire, Motorola Droid Razr, and LG Optimus Black. 

However, WhatsApp will function on phones with KaiOS 2.5.1 OS or newer versions such as JioPhone and JioPhone 2. 

How to check out the operating system your phone is running on?  

For Android users: Go to Settings, then select About System, and there you will see the Android version installed on your smartphone. 

For iPhone users: Go to the Setting menu, then to the General option and select Information, there you will get details about the software version your iPhone is running on. 

People who have the option to update the operating system can use WhatsApp. But people who do not have that option will have to buy a new phone to use WhatsApp.