Apologies for the lousy formatting of the above: FF killed the line breaks when I submitted the post. That too is a bug that needs fixing. Hope this version is clearer.

I have tried:

—clearing history and cookies, rebooting computer, and opening FF with no other program open yet: crash.

—being signed in to FF to sync bookmarks: crash.

—not being signed in to FF: crash.

—closing all windows before quitting: crash.

—windows open at quitting: crash.

—verifying legacy app booleans in about:config were set to defaults (they were): crash.

—wifi on, or wifi off: crash.

Forgot one more thing: crashes occurring on varied ISPs--two different work campuses, and my home network. So not a specific network issue.

Plug-in: Flash Add-ons: NoScript 5.1.1 Add-on Compatibility Reporter 2.2.4 Adblock Plus 2.9.1 FlashStopper 2.4.9

Forgot to mention: still crashes in SAFE MODE.

hi, firefox 56 fixed a bug where some offline-data wasn't properly purged even though it was set in the options. probably what you're seeing now is firefox trying to clear that amounted data during shutdown but taking too long (if it's still running 60secs after you close it there will be this artificial crash triggered that you're seeing).

can you try to clear all offline-website data and the cache and let that dialog sit until its done?

I was long on the FF 56 beta, so that should have already been closed, but I tried this anyway, setting it to clear time range/everything and details/all. It is still saying 'clearing' 5 minutes after I asked it to clear, with both 'clearing' and 'cancel' buttons grayed out.

How long is it reasonable to wait for this 'clearing' process to complete?

this was landed very late in the beta phase (into one of the last release candidates). i can't really say how long it should reasonably take, but if it's too bothersome i'd do it when you are away from the pc for a bit. if you keep letting it go and observe how long it would take all in all that might be an interesting bit of information for us that might help in getting the bug addressed: https://bugzilla.mozilla.org/show_bug.cgi?id=1404105

I'm letting it go, because I have to step away from the computer for a few hours anyway, but it's up to 30 minutes now and not showing signs of stopping.

Any idea what the 'clearing' process should look like in Activity Monitor? FF shows as open but not active when I look there. (MBP running El Capitan)

i am not sure because i can't reproduce the problem in my setup, but i'd imagine there should certainly be some disk activity going on during the cleaning

I left the computer for 4 hours, returned, and the 'clearing' window was still there. I forced a quit, and then checked clearing by different times and items clicked to clear in the 'clear recent history' dialog, and it hangs--and thus I suspect would be creating a crash as described above because it doesn't quit due to the hang--when 'offline website data' is checked, regardless of whether it is clear for last hour--and FF is freshly opened--or 'everything [all time]'.

This must be what is causing my crashes on quit, because my standard FF configuration is to clear history on closing including

Browsing & download history Active logins Form & search history cookies cache offline website data

So it's choking on the 'offline website data' command every time.

BTW, is there a limit to how many 'helpful' posts I can credit in a thread like this? I know at Apple discussions it's 2 helpfuls plus 1 solved per thread, so I hold back on the helpfuls until it is solved....

Still asking: how to stop FF from crashing every single time I ask it to clear offline website data?

Could you confirm which version you are running please as Firefox was/will update this date to version 56.0.1  ??

You have a FlashStopper running and have Flash version 26 installed. If not using Flash uninstall, if using it please update it to current version 27 https://get.adobe.com/flashplayer/otherversions/ Step 1: Select Operating System Step 2: Select A Version (Firefox, Win IE . . . .) Note: Other software is offered in the download. <Windows Only>

Fyi: you will loose all legacy addons/Extensions when Firefox 57 Quantum is released on November 14th. You may want to consider going to the Extended Release version so you can continue using your Extensions : https://www.mozilla.org/en-US/firefox/organizations/all/

So please update Flash as that can be a issue, update https://support.mozilla.org/en-US/kb/upgrade-graphics-drivers-use-hardware-acceleration#w_after-upgrading-your-graphics-driver and try No Hardware Acceleration

Before continue might want to think of using CCleaner or something ?? Also may want to think about Nov 14th and loosing extensions no matter what... So might be better if install the Extended Release now ??

Please let us know if this solved your issue or if need further assistance.

FF 56.0 which says it is up to date.

Flash version is 27 now.

Add-ons are auto-updating, so as up to date as are available.

My extensions are not yet updating themselves to FF57 compatible versions and I am not prepared to surf the web without them—that is the whole point of FF, the ability to make the web quieter, less jangly, and safer—so not going to 57 yet. NoScript will be updated by the time of the 57 release, so I am waiting for it to update before I will go to 57.

If you can suggest widely-used and well-reviewed ad-ons that are equally effective as those I’m using, I’m happy to hear about them.

CCleaner? Do you think this crash problem means I have a virus?

Nothing was working, had to Refresh Firefox. Now working with lost preferences. Such a frustrating waste of time.

Look on your desktop. Do you see a folder called; Old Firefox?

https://support.mozilla.org/en-US/kb/recovering-important-data-from-an-old-profile

https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles

https://support.mozilla.org/en-US/kb/how-run-firefox-when-profile-missing-inaccessible

Thanks for the reminder. I pulled my prefs.js and userChrome.css from the old profile on the backup machine and reinstalled them, and FF still opens and quits without the crash. Whew.

Now just waiting for NoScript etc come up with FF57 compatible versions, and then I'll move on up.

Thanks, Philipp. Clearing the cache resolved the crashing on quit (had to Force Quit every time) did the trick for me!

Firefox > Preferences > Cached Web Content > Clear now

Much appreciated!

philipp said

hi, firefox 56 fixed a bug where some offline-data wasn't properly purged even though it was set in the options. probably what you're seeing now is firefox trying to clear that amounted data during shutdown but taking too long (if it's still running 60secs after you close it there will be this artificial crash triggered that you're seeing). can you try to clear all offline-website data and the cache and let that dialog sit until its done?