Hello etg,

In Settings => Default apps : when you click on one of the listed apps, a dialog should appear - doesn't it show Firefox as an option  ?

Firefox doesn't show - only Edge, Internet explorer and 'look for an app'.

etg said

Firefox doesn't show - only Edge, Internet explorer and 'look for an app'.

Clicking on one of them doesn't bring up a dialog that does show Firefox as an option  ?

Another thing you can try is to re-install Firefox if "Look for an App" doesn't show Firefox

Probably a redundant remark, but if you do need to re-install Firefox, please make sure that in Settings => Apps you have it set to "Allow all apps" .....

(edit : typo .... )

Thanks for your reply. Do I need to uninstall before re-installing? In either case, what happens to bookmarks, history, settings and add-ons; is it possible to back these up?

etg said

Thanks for your reply. Do I need to uninstall before re-installing? In either case, what happens to bookmarks, history, settings and add-ons; is it possible to back these up?

When you perform a Clean reinstall it means you remove your Firefox program files and then reinstall Firefox. This process does not remove your Firefox profile data (such as bookmarks and passwords), since that information is stored in a different location.

To do a clean reinstall of Firefox, please follow these steps:
Note: You might want to print these steps or view them in another browser.

1. Download the latest Desktop version of Firefox from mozilla.org (or choose the download for your operating system and language from this page) and save the setup file to your computer.
2. After the download finishes, close all Firefox windows (or open the Firefox menu and click the close button ).
3. Delete the Firefox installation folder, which is located in one of these locations, by default:
   • Windows: (Note: Check both folders.)
     • C:\Program Files\Mozilla Firefox
     • C:\Program Files (x86)\Mozilla Firefox

Now, go ahead and reinstall Firefox:

1. Double-click the downloaded installation file and go through the steps of the installation wizard.
2. Once the wizard is finished, choose to directly open Firefox after clicking the Finish button.

More information about reinstalling Firefox can be found here.

WARNING: Do not use a third party uninstaller as part of this process. Doing so could permanently delete your Firefox profile data, including but not limited to, extensions, cache, cookies, bookmarks, personal settings and saved passwords. These cannot be easily recovered unless they have been backed up to an external device! See  : Back up and restore information in Firefox profiles.

Like I said before : please make sure that in Windows Settings => Apps you have it set to "Allow all apps" .....