Update, October 24 (problem persists): Firefox continued to hang upon trying to connect to Google (my go-to test website), and then requires me to Force Quit. Deleted the Firefox app and all Firefox items from the Library, plus a bunch of other legacy items that were empty folders or do not work with Sonoma.

Downloaded and ran trial version of Malwarebytes, found and quarantined one non-dangerous item, but could not launch the Real-Time Protection (solution for that found later).

Following suggestions on Malwarebytes website, I completely reinstalled OS 14.4 (Sonoma) [glad that I had a few hours worth of planting and pruning to do while it installed!], ran Malwarebytes again (found and quarantined a second non-dangerous item), then found a page on Malwarebytes that said the reason I could not launch Real-Time Protection was that I had to give that app full disk access, which I did (System Settings > Privacy & Security > Full Disk Access > toggle on Malwarebytes Protection).

Fortunately Safari works just fine (the Chrome browser also works), which allowed me to download and install a brand new version of Firefox, which immediately proceeded to hang when I tried to go to Google.com. I had to Force Quit the app, which resulted in yet another (now probably over a dozen) crash report to be submitted to Apple.

Hi Julian, was Firefox running normally on your system before Firefox 124/MacOS 14.4, or is this your first installation of Firefox?

Aside from the regular release (so-called rapid release), Firefox has an Extended Support Release (ESR) which is based on a version from last fall. You could download the DMG for ESR and see whether it will install and run normally on your system.

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

Brilliant, jscher2000. Firefox is now working.

To answer your question: I've been using Firefox on Mac OS for years with no problem. In the last few days I did upgrade to OS Sonoma--I do not recall whether Firefox quit working *immediately*, or within a few days. Good call on your part, as that may have been the problem.

I deleted my most recent installation of Firefox and its library, then downloaded and installed the Extended Support Release version of Firefox that you suggested. I tried to visit Google.com, but when Firefox was taking a long time to connect (as happened on every previous attempt) I thought that we had failed once again.

I then stopped the attempt to reach Google and clicked on "About Firefox," where the message said that Firefox was checking for updates. That was taking a long time, so I let the process continue while I left to watch TV for an a couple of hours.

I'm glad that I didn't give up too soon. When I returned after a couple of hours the "About Firefox" window message said that "Firefox is up to date": 115.9.1esr (64 bit)., which I think is the same version I saw when I first launched it, before it checked for updates.

I then imported my bookmarks back from Safari, where I had imported them from Firefox, and now I just to spend a little time checking my Firefox settings. I had also exported my passwords which I'll import tomorrow when I'm fresh.

Thank you again for taking the time to help a tired and frustrated user.

Julian

I'm back, and the problem remains. What was thought to be a solution was only fleeting, so I have been using Safari ever since.

I'm using Mac OS 14.5 Sonoma. As I recall, Firefox (which I've been using for years) quit working about the time that I upgraded to Sonoma, but I can't be sure of the sequence of events.

I have just returned from vacation and have downloaded a fresh install of Firefox 126, and it still hangs upon launch while "checking for updates" and cannot open any websites. Soon the whirling pizza of death appears and I have to Force Quit.

(The home screen still includes the Twitter app button, instead of X--screenshot attached; could this have something to do with the problem?)

In the initial setup I skipped the prompts (default browser, import bookmarks, etc.

I can upload a copy of the crash report if that will be of any help to anyone who knows more about computers than I do, which is pretty much everyone.

I can live with Safari, and have been doing so for a couple of months, but I'd really, really like to get Firefox running again for me.

Hi Julian, I'm not familiar with what type of crash data is available when you force quit an app on Mac. Hopefully another support volunteer could comment on that.

There was a problem with Firefox updates failing when NordVPN was installed, but I think NordVPN fixed that in an update. If you have NordVPN but don't update it often, please update it now before testing again.

Welcome back, jscher2000. Thank you for continuing to hold my hand. I do not have NordVPN.

So fingers crossed that someone can come up with a solution.