Sorry to hear about the crashes and thank you for the report number. That page says:

MOZ_CRASH Reason (Sanitized): Failed to get Omnijar AppJar archive for entry (path: "chrome/browser/content/browser/built_in_addons.json")

This sounds like your program files got corrupted somehow. Coincidentally, there is a new version of Firefox out today, Firefox 101.0. I suggest trying to install Firefox 101.0 over your existing installation to see whether the updater is able to repair the files. You can download the "full" installer from the following page:

https://www.mozilla.org/en-US/firefox/all/#product-desktop-release

The page should automatically select Windows 64-bit, but if it doesn't please select that to make sure you are replacing your current release type with the same one.

Does that fix it?

Thanks for your response - unfortunately this did not fix the problem, when I finished the installation and selected launch firefox, there was a brief flicker of an icon on the taskbar that quickly vanished - presumably crashing again.

Any luck trying to start Firefox in its Troubleshoot Mode:

Hold down the Shift key when starting Firefox using its Desktop icon or Taskbar button.

Firefox should show a little dialog giving two choices, pick Troubleshoot Mode, not Refresh.

Any improvement?

Unfortunately not, even when starting in troubleshoot mode there is no response. I can see on task manager that there is a firefox process open, currently running at just below 50mb ram, but no sign of it on the taskbar or in task view.

Do a clean reinstall of the current Firefox release and delete the Firefox program folder before installing a fresh copy of the current Firefox release.

• download the Firefox installer and save the file to the desktop
  *https://www.mozilla.org/en-US/firefox/all/#product-desktop-release

If possible uninstall your current Firefox version to cleanup the Windows Registry and settings in security software.

• do NOT remove "personal data" when you uninstall the current Firefox version, because this will remove all profile folders and you lose personal data like bookmarks and passwords including personal data in profiles created by other Firefox versions

Remove the Firefox program folder before installing that newly downloaded copy of the Firefox installer.

• (64-bit Firefox) "C:\Program Files\Mozilla Firefox\"
• (32-bit Firefox) "C:\Program Files (x86)\Mozilla Firefox\"

• it is important to delete the Firefox program folder to remove all the files and make sure there are no problems with files that were leftover after uninstalling

Your personal data like bookmarks is stored in the Firefox profile folder, so you won't lose personal data when you reinstall or update Firefox, but make sure NOT to remove personal data when you uninstall Firefox as that will remove all Firefox profile folders and you lose your personal data.

If you keep having problems then you can create a new profile as a quick test to see if your current profile is causing the problem.

• https://support.mozilla.org/en-US/kb/profiles-where-firefox-stores-user-data
• https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles

Reinstall Firefox

• https://support.mozilla.org/en-US/kb/troubleshoot-and-diagnose-firefox-problems