Windows application completely failing

Hello, to figure out what's causing your problem, try disabling all your extensions. Launch Firefox—if it works, the issue is caused by an extension. If that doesn’t solve your problem, try uninstalling Firefox completely. Go to the application’s settings, search for Firefox, uninstall it, and then reinstall it from the official website using the latest version. If the Firefox icon on the Windows taskbar doesn’t disappear after you uninstall it, remove it manually (right-click on it and select “Unpin from the taskbar”), then reinstall Firefox. Let me know if that solved your problem.

I’ve already done all of this and what extensions I had were deleted by the reinstallation. If it helps, my installation of Google Chrome also seems to be behaving similarly

My Firefox has very recently been having an extreme error in which the shortcut will not launch it, and when launched via running as administrator, I get a blank, grey background instead of any website I try to open. Refreshing via the uninstaller and a new install have not helped

Hi Connor, when Firefox's "parent" process runs but "child" processes do not work, the most common historical explanation has been security software, particularly anti-exploit software, tussling with Firefox over whether the security software could inject a DLL into Firefox's processes. Some past examples are mentioned in "Firefox won't start - find solutions" but this probably does not include conflicts arising from the most recent updates.

In a very quick look at Bugzilla, I didn't see a related-looking bug. You may want to file a new one. https://bugzilla.mozilla.org/

For the sake of completeness, have you tested starting up in Firefox's Troubleshoot Mode? In that mode, Firefox temporarily deactivates extensions, hardware acceleration, any userChrome.css/userContent.css files, and some other advanced features to help you assess whether these are causing the problem.

While Firefox is running:

You may be able to restart Firefox in Troubleshoot Mode using either:

• "3-bar" menu button > Help > Troubleshoot Mode...
• (menu bar/Alt+H) Help menu > Troubleshoot Mode...

and OK the restart. A small dialog should appear. Click the Open button.

If Firefox is not running:

Hold down the Shift key when starting Firefox. (On Mac, hold down the option/alt key instead of the Shift key.) A small dialog should appear. Click the Open button.

Note: Don't use Refresh again.

Any improvement?

Ref. Use Troubleshoot Mode in Firefox

Troubleshooting mode does “work” insofar as being able to activate it, however it doesn’t give different results, I think possibly because everything it deactivates is already not being used. I’ve also tried running it with windows’ firewall broadly disabled, but seeing as that’s provided no progress it may require a more specific fix

Hi Connor, thank you for testing that. One of the challenges for support volunteers in this situation is that the usual places to check for information are not available yet because Firefox is stalled during startup. You could look at the Browser Console (Ctrl+Shift+J) to see whether it will load and whether it has any error messages yet. It's possible we'll recognize something, but more likely it would be to share in the bug report.

Unfortunately Firefox doesn’t load even through running as admin now, so will have to take this further

Can you try getting a copy installed from Microsoft Store, to see if that one launches?

Download Firefox on Windows from the Microsoft Store

This has worked (was not aware that the MS store had Firefox). I can use this copy in the meantime but would still like to resolve the initial issue fully