It cannot. Enumerating protocol handlers is actually an excellent fingerprinting technique. That’s why platforms like iOS for instance forbid it, or you have to

It cannot. Enumerating protocol handlers is actually an excellent fingerprinting technique. That’s why platforms like iOS for instance forbid it, or you have to explicitly specify which ones you’ll query (see: https://developer.apple.com/documentation/uikit/uiapplication/1622952-canopenurl https://developer.apple.com/documentation/uikit/uiapplicatio...).