I wonder whether this is a Visual C Runtime problem? That can make Firefox useless from the address bar down. Even if you haven't seen a message related to a missing VCRUNTIME140_1.DLL file, it may be worth (re)running Microsoft's installer for the VC Runtime files:

(A) Open https://docs.microsoft.com/en-US/cpp/windows/latest-supported-vc-redist?view=msvc-160#visual-studio-2015-2017-2019-and-2022

(B) In the "Visual Studio 2015, 2017, 2019, and 2022" section of the article, download the installer for your system:

• 64-bit Windows: the "X64" download
• 32-bit Windows: the "X86" download

(C) Run that installer and restart Windows.

Any improvement?

A couple of other users identified Webroot (security software) as blocking Firefox 97 from running properly:

• https://support.mozilla.org/questions/1367248
• https://support.mozilla.org/questions/1367301

Is that a potential factor on your system?

I just found out I have the exact same problem at work. The problem there is that I cannot find any MS updates that aren't less than a month old. I have not yet verified the C++ re-install does anything at home. I ran the installer just before leaving for work and let the computer reboot. I did just run the installer on the work computer and No Joy on fixing the problem.

Both home and work computers DO run Webroot. I am about to look at the other questions to see what I can glean from them.

There is a mitigation for the conflict in Firefox 98, now in beta testing. You can confirm by installing Firefox Developer Edition, which will sit alongside regular Firefox and use its own profile folder.

If all goes well with the patch, we can hope it will be added to a Firefox 97.0.1 update. For now, though, I don't have a way to make 64-bit Firefox 97 work with the combination of Webroot plus yesterday's Windows update.

Forgot the link: https://www.mozilla.org/firefox/developer/

According to a user post in an active bug report, another workaround would be to run Firefox 97 in backwards compatibility mode. I haven't tested this myself, but here is how you would set that up:

(1) Open the Properties dialog for your Firefox shortcut. Either:

• right-click a Desktop shortcut, then click Properties
• right-click a pinned Taskbar icon, then right-click the Firefox (or Mozilla Firefox) item, then click Properties

(2) Switch to the Compatibility tab

(3) Check the box for "Run this program in compatibility mode for"

(4) If the selector for that option is not set on Windows 8, switch it to Windows 8

As a result of this change, you may notice that some Windows 10-specific features and styling are disabled. However, I am not aware of any major changes. If you experiment with this, let us know your experience.

I have been having this exact problem (Webroot, MS update, & Firefox). I tried the backwards compatibility fix and it does allow me to run Firefox now (thank you).

However, I am not able to run my password manager (1Password) extension. It shows the extension is there and enabled but the icon is not in the toolbar and the functionality is not there.

I have been having this exact problem (Webroot, MS update, & Firefox). I tried the backwards compatibility fix and it does allow me to run Firefox now (thank you). However, I am not able to run my password manager (1Password) extension. It shows the extension is there and enabled but the icon is not in the toolbar and the functionality is not there.

I think the 1Password add-on may need to communicate with another program on your computer. I'm not sure why that isn't working in compatibility mode or with the latest Webroot.

A few users have now confirmed that uninstalling and reinstalling Webroot worked for them, so if you are allowed to do that (not restricted by an IT department), you could try that next and see whether it lets you run without compatibility mode.

https://www.mozilla.org/firefox/97.0.1/releasenotes/

Fixed Works around problems with WebRoot SecureAnywhere antivirus rendering Firefox unusable in some situations

Installed 97.0.1 from the current Beta. All seems well!

I uninstalled and re-installed the 1Password add-on and it worked.