Right now, we assume that any app packaged browser is Edge/Edgium. With the Microsoft Store now open to additional browsers, that's no longer true -- in particular, Firefox could be the app packaged browser! This ticket tracks unwinding the AppID values like AppX... to figure out what the browser really is.

I've not found any documentation on this yet, but it looks like each MSIX Application that registers for a file association (or a protocol handler) gets an AppX... AppID generated. Those AppIDs are then used in the regular registry locations, like:

Computer\HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\FileExts\.pdf

One can find the details in the usual place, like:

Computer\HKEY_CLASSES_ROOT\AppX...\Application

and from there find package details in AppUserModelID, which always appears to be the package family name.

I'm not sure if the generated AppID is:

• per-package name (including version, etc)
• per-package family name (not including version, etc)
• per-device
• per-installation

But hopefully none of that really matters, and the registry entries let us figure everything out.

This changes the heuristic used to identify the Windows default browser. In this the ProgID for the default http protocol handler is used to find an associated Friendly Name. This is campared with known prefixes for tracked browsers.

Special casing is added to track Edge Legacy and Edgium separately.

https://hg.mozilla.org/mozilla-central/rev/0db83eed57da