Use a web browser to access WhatsApp Web . However, the native Safari on iOS 7.1.2 is too outdated to render it; you would likely need a third-party legacy browser if any still support modern web standards.

WhatsApp sometimes officially kills support for very old versions. While 2.12.15 is robust, it may eventually show a "Please update this app" message.

You can no longer use the official WhatsApp application on iOS 7.1.2 because WhatsApp permanently dropped support for this operating system. If you try to install it from the App Store, you will encounter compatibility errors, and existing installations will fail to connect to WhatsApp servers due to outdated security protocols.

Therefore, the two most viable modern options are AltStore and Sideloadly.