Just a thought: I suspect that this has something to do with me modifying a setting on about:config, but I don't know what exactly.

Hi Cecile, anything you changed in about:config would be wiped away by the Firefox Refresh feature, so that would be difficult to investigate right now. I assume you still have the Old Firefox Data folder on your desktop for future reference?

Could you try starting Firefox in its Safe Mode? That temporarily deactivates extensions, hardware acceleration, and some other advanced features to help you assess whether these are causing the problem.

If Firefox is not running: Hold down the option/alt key when starting Firefox.

If Firefox is running: You can restart Firefox in Safe Mode using either:

• "3-bar" menu button > "?" button > Restart with Add-ons Disabled
• Help menu > Restart with Add-ons Disabled

and OK the restart.

Both scenarios: A small dialog should appear. Click "Start in Safe Mode" (not Refresh).

Any improvement?

As a Windows user, I'm not sure I have a lot of insight into Mac startup crashes.

Dear jsher2000,

I have tried starting in safe mode already but the problem is still there... Yep I have some old firefox data but I am not sure what I should do with it? Can I reinstall some older config?

Thanks for your help! Cecile

I looked at the crash report you shared and nothing leaped out at me, except that on the Modules tab, many files have a weirdly low version number:

https://crash-stats.mozilla.com/report/index/bp-85d0dd69-7732-4f44-b424-2fb7a0171031

But as I said, I'm a Windows user, so for all I know, that's normal on Mac.

Could you share a few more crash report IDs? Please check the support article "Firefox crashes - asking for support" for steps to get those crash report IDs from the about:crashes page or from disk if Firefox won't run long enough to use about:crashes.

Here you go: Crash ID: bp-8cd3d46b-d1f0-4400-9bcf-d397b2150401 Crash ID: bp-5d3d6052-c15d-4218-8836-5b1522150713 Crash ID: bp-4f328f7d-6f60-46e9-a1be-8fb961171031 Crash ID: bp-4c725f4a-6eca-40c9-a794-bcd081171031 Crash ID: bp-2cbeb950-1c31-4151-bcfb-3f8072160914 Crash ID: bp-1d3db7de-2d4c-483d-9acb-0e4a81171031 Crash ID: bp-1a2ade7a-92e6-422c-8f7b-f04dd1171031 Crash ID: bp-0c95c78d-f9ff-414f-8c62-13edf1171031 Thanks a lot again for your help! Cecile

This could be a sandbox issue.

Try to modify this pref on the about:config page to disable the sandbox to see if that has effect.

• security.sandbox.content.level = 0

You can open the about:config page via the location/address bar. You can accept the warning and click "I accept the risk!" to continue.

• http://kb.mozillazine.org/about:config

See also the attached bug report comment 25.

• bug 1404298 - When Running Firefox Stable and Firefox Developer Edition together, eventually tabs begin crashing

(please do not comment in bug reports
https://bugzilla.mozilla.org/page.cgi?id=etiquette.html)

Dear cor-el,

Thanks a lot, this indeed solved the problem! It seems to be running stable now.

Have a good day all and thanks again, Cecile

You're welcome.

Maybe keep an eye of this bug report and re-enable the security sandbox via the right-click context menu once you update to a Firefox version that fixes this problem.