Is it possible to detect whether whatsapp is installed?

Question

On an iPhone device, on an HTML page you can always compose an sms (via an sms:1234567890 URL), and if WhatsApp is installed, you can compose a WhatsApp message (via the WhatsApp protocol).

Is it possible to detect such features on an HTML page?

Answer 1

Following a few hours of research + consulting with top experts I came to the conclusion that there is no legitimate way of achieving the goal of detecting whether a specific app is installed on the device without having the browser re-direct to the app if it is installed.

In iOS for example, there was an app just removed from the App Store because of violating the rules: SysSecInfo. The app managed to pull list of all running processes for example.

From: https://www.sektioneins.de/en/blog/16-05-09-system-and-security-info.html

See https://developer.apple.com/videos/play/wwdc2015/703/ "App Detection" starting at 08:34

During this talk they discuss several APIs used to gather information about processes currently running on your system (around 12:12 in the video) and claimed to have fixed them. However as so often Apple has only partially fixed the problems they claim to have fixed. Therefore they have actually never stopped malicious applications from gathering information about what other applications run currently on your device, but only removed access to detail information that is only relevant for harmless system information tools anyway.

System and Security Info is therefore still able to show the list of running processes and enriches this list with information from the codesigning information including the list of entitlements running processes have.