While WhatsApp already has a public beta version for both Android and Windows Phone users, it does not have a public beta version for iOS users. Over the years, WhatsApp has been restrictive about who uses WhatsApp for iOS beta. However, that is set to change now as the beta version for iOS users has been made public. So from now on, all iOS users will be able to test features on the beta version of WhatsApp before they are being rolled out in a stable version. In order to download WhatsApp for iOS beta, the users need to first download TestFlight from the Apple App Store.
After you download and install TestFlight from the Apple App store, you should click on the link here to get a beta slot as reported by WABetaInfo. Now, download and install the beta app on your phone. Once you click Install, a dialog box will appear asking you whether you want to replace the existing version of WhatsApp with the beta version. You should hit install to start the process of installation. The report further states that slots for WhatsApp for iOS beta are very limited so the users must download it as soon as possible.
Once the installation is completed, tap open to launch the beta app. It is recommended to take a backup of your chat history before installing the beta app to prevent any accidental deletion of data. Just like other TestFlight based beta apps, the number of slots available is limited and hence only a handful of people are provided access to it. So, if you want to download the beta app, you should do it as soon as possible.
The report further suggests that WhatsApp for iOS beta receives updates every two days to incorporate newer features before they are rolled out publicly. However, the beta version of the app may contain certain bugs and is prone to crashing. So you should download the updates with caution.