The messaging giant - which is owned by Facebook Inc - will stop working for users whose phones are too old to upgrade, meaning they will have to update the actual device and those with devices capable of upgrading the software will have to do so to regain access.
The FAQ section of the WhatsApp website reads: "We provide support for and recommend using the following devices: Android running OS 4.1 and newer
iPhone running iOS 10 and newer
KaiOS 2.5.0 and newer, including JioPhone and JioPhone 2
Once you have one of these devices, install WhatsApp and register your phone number. WhatsApp can only be activated with one phone number on one device at a time."
Devices that are too old to be upgraded - of which there are 52 in total - include Samsung Galaxy S3, Samsung Galaxy Trend Lite, Galaxy Trend II, Galaxy SII, Galaxy S3 mini, Galaxy Xcover 2, Galaxy Core and Galaxy Ace 2, the Huawei Ascend Mate and the iPhone 4S.
Those phones are too old to upgrade to the operating systems necessary to run the latest version of WhatsApp, but users of phones such as the iPhone 6S onwards should be able to just update the software.
Users needing to upgrade either handsets or software are encouraged to do so because avoiding upgrades can pose a security risk.
Software upgrade options can usually be found in the 'Settings' section of most handsets.
It comes shortly after the messaging app added an "extra layer of security" in the form of an encryption of messages backed up to Google Drive or iCloud.
In a blog post, the comapny explained: "‘While end-to-end encrypted messages you send and receive are stored on your device, many people also want a way to back up their chats in case they lose their phone.
Starting today, we are making available an extra, optional layer of security to protect back-ups stored on Google Drive or iCloud with end-to-end encryption. No other global messaging service at this scale provides this level of security for their users’ messages, media, voice messages, video calls, and chat back-ups."