How to find URL Scheme from .ipa file

First, unzip the .ipa file. (you can rename it with .zip to do this).

Then, inside the .ipa file, you will find there is a Info.plist file. 

You can parse that file, look for "CFBundleURLSchemes" and you will see first the app id followed by the Custom URL if one is defined for the app.

Source: http://stackoverflow.com/questions/6845693/can-i-extract-the-custom-url-scheme-from-a-ipa-file