How to use ua:// URLs There are buttons in the Starbucks app on iOS for redeeming free apps and if I long press on the button, it shows a URL like ua://75A6A5DC-D3BE-4056-9482-CEBCD5493F98. However, I don't know how to use the URL if I copy it. Safari won't navigate anywhere if I paste it in the address bar and press Go. If I just tap the button in the Starbucks app, it takes me to the App Store and automatically begins to redeem an app (presumably using a code embedded in, or retrieved from, the ua:// URL, but I'm not sure on that—just my hypothesis).

I have Googled and can't find any information on the ua URI. Can someone link me to documentation on what it means and how to use links like that?
When you click the button, iOS looks for an app that advertises itself as being able to handle ua://-URLs. Safari doesn't know how to do that, you'll need an app for that. I don't know if there's a way to find out which app responds to which URL schemes.
See this developer article.