+++ This bug was initially created as a clone of Bug #1703578 +++

These articles will need updating for Firefox 91:
https://support.mozilla.org/en-US/kb/how-change-your-default-browser-windows-10
https://support.mozilla.org/en-US/kb/make-firefox-your-default-browser

Related discussion:
https://support.mozilla.org/en-US/forums/contributors/715221#post-81895 Firefox 91 for Desktop - Release Notes / Issues / Discussions
https://support.mozilla.org/en-US/kb/how-change-your-default-browser-windows-10/discuss/9972#post-21945

Firefox uses an undocumented way to make it as default without using Settings. Microsoft may break the way in the future. In that case, Firefox will open Settings as a fallback. So the article should explain about that possibility.

Fabi, Revisions have been made to the two articles by Julie, a new contributor. Can you review?
https://support.mozilla.org/en-US/kb/how-change-your-default-browser-windows-10/history
https://support.mozilla.org/en-US/kb/make-firefox-your-default-browser/history

Related discussion in https://chat.mozilla.org/#/room/#sumo:mozilla.org

:emk is correct, we may be able to silently change the defaults, but this does not always work for various reasons, and may stop working altogether in the future, so the Settings dialog may still be shown on 91 and up. We'll try opening Settings if there was an error or if there's a 2 second timeout. I'd suggest something like:

3. Firefox may now be listed as your default browser.
4. Otherwise, the Windows Settings app will open with the Choose default apps screen.

I regret how confusing this is.

The early planning document linked in bug 1703578 doesn't provide any relevant details, sorry about including that link in the public bug.

Reopened based on comment 4.

(from comment #0)

These articles will need updating for Firefox 91:
https://support.mozilla.org/en-US/kb/how-change-your-default-browser-windows-10
https://support.mozilla.org/en-US/kb/make-firefox-your-default-browser

(In reply to Adam Gashlin (he/him) [:agashlin] (ex-moco) from comment #4)

:emk is correct, we may be able to silently change the defaults, but this does not always work for various reasons, and may stop working altogether in the future, so the Settings dialog may still be shown on 91 and up. We'll try opening Settings if there was an error or if there's a 2 second timeout. I'd suggest something like:

3. Firefox may now be listed as your default browser.
4. Otherwise, the Windows Settings app will open with the Choose default apps screen.

I regret how confusing this is.

The early planning document linked in bug 1703578 doesn't provide any relevant details, sorry about including that link in the public bug.

Both articles have been updated recently, with Windows 11 information added. The first article was also renamed https://support.mozilla.org/en-US/kb/how-change-your-default-browser-windows ("10" was removed from the title) since it also applies to Windows 11.

I'm just not sure if the Windows "Settings" dialog will also open up in Windows 11 if the [Make Default] button in Firefox about:preferences doesn't work. Can someone confirm what happens on Windows 11?

Yes, the Windows "Settings" dialog will open up in Windows 11. You can easily confirm that by yourself using MSIX packaged Firefox. One-click default does not work with MSIX packaged Firefox.

Also, one-click default is not supported on Windows 8. The control panel will show up.

(In reply to Masatoshi Kimura [:emk] from comment #7)

Yes, the Windows "Settings" dialog will open up in Windows 11. You can easily confirm that by yourself using MSIX packaged Firefox. One-click default does not work with MSIX packaged Firefox.

Thanks for answering and for the information that on-click default is not supported on Windows 8. I posted that question before in a SUMO kbforum but never got an answer.
Just to be crystal clear:

1. When you say that one-click default does not work and the Settings Dialog will open with MSIX packages (i.e. installed from the Microsoft Store) I'm assuming that includes Windows 10 as well as Windows 11.
2. When Firefox is installed from a Mozilla download, one-click default will mostly work on Windows 11, as it does on Windows 10.

Thanks again.