topic Re: Firefox freezing after upgrade to 146.0 in Discussions

Firefox freezing after upgrade to 146.0

MPV — Wed, 10 Dec 2025 22:22:25 GMT

After sleeping or locking screen, I find the Firefox browser is freezed, unsensitive to any action. This is happening systematically after upgrading to version 146.0. It had never happened to me before that upgrade. Any suggestions? Thanks!

Re: Firefox freezing after upgrade to 146.0

siffemcon — Wed, 10 Dec 2025 23:58:50 GMT

Does that also happen in Troubleshoot mode (https://support.mozilla.org/en-US/kb/diagnose-firefox-issues-using-troubleshoot-mode/)?

Re: Firefox freezing after upgrade to 146.0

JulesA — Thu, 11 Dec 2025 19:56:07 GMT

Yes, it's REALLY, REALLY BAD. The browser is almost not useable anymore. Constantly freezes up, freezes when you try to type into fields, YouTube is very difficult to use with the update. It's a terrible browser. The worse changes were about a year ago which made me use an older browser, but now its beyond bad.

Re: Firefox freezing after upgrade to 146.0

JulesA — Thu, 11 Dec 2025 19:57:09 GMT

I have the same issue. Terrible browser now. Makes no difference if its in troubleshoot mode or not. They're ruining Firefox with each update...

Re: Firefox freezing after upgrade to 146.0

forrie — Thu, 18 Dec 2025 16:51:06 GMT

I have been experiencing similar issues, on MacOS Sequoia, and it's really interfering with my regular use of the browser.

I have brought the browser into Safe Mode and felt the same issues were present. The information available in about:processes could be better. For example, under Extensions, I'd like to see a breakdown of which extension is active and what % resources it's consuming. Each time I run this, however, the only process that is really high is Firefox itself.

Yes, I do have several tabs open. But, when this happens, I will kill off the Firefox process, restart/restore, and even with inactive tabs, the problem persists.

I do use uBlockOrigin and I suspected this may be part of the issue, but I cannot confirm it. At least, not with the debugging I've been able to do.

This problem seemed to present in the recent builds, as I've not really added much to it.

I take the same URLs and insert them into another browser and it works fine, granted in at least Chrome, I cannot run a full uBlockOrigin due to their recent changes, so I can't fully duplicate.

I "could" downgrade the version of Firefox, but that would take bit of effort (I have a lot of bookmarks, etc) and I don't really want to lose my active session cookies.

That being said, do we understand what the specific issues are or may be, and what additional steps might be useful to help debug? A search shows there are various similar reports, but I cannot substantiate them.

Re: Firefox freezing after upgrade to 146.0

zaufi — Sun, 21 Dec 2025 22:49:28 GMT

Also faced with freezes 😞 146 and 146.0.1 affected.

It just become irresponsible after some short time after start.

Re: Firefox freezing after upgrade to 146.0

MPV — Mon, 22 Dec 2025 21:02:45 GMT

Yes, it happens also in Troubleshoot mode

Re: Firefox freezing after upgrade to 146.0

forrie — Sun, 28 Dec 2025 18:09:07 GMT

I have observed the processes on MacOS, via Activity Monitor. When I see FirefoxCP Webextensions using 30% or more CPU, Firefox itself begins to climb -- I've seen it use more than 100%.

If I go to about:processes, I cannot see a way to drill down into individual web extensions, to identify any problems therein. Is there some way to do this with Firefox?

Re: Firefox freezing after upgrade to 146.0

Agentvirtuel — Mon, 29 Dec 2025 09:10:54 GMT

Hello

https://support.mozilla.org/en-US/kb/file-bug-report-or-feature-request-mozilla
If you wish, you can send your comment, file a bug report.

Components Firefox.
https://bugzilla.mozilla.org/describecomponents.cgi?product=Firefox

Task Manager - see whether tabs or extensions are slowing down Firefox.
https://support.mozilla.org/en-US/kb/task-manager-tabs-or-extensions-are-slowing-firefox
Firefox Profiler https://profiler.firefox.com/docs/#/./guide-getting-started
For information purposes, with your report, you can share a profile.
https://firefox-source-docs.mozilla.org/performance/reporting_a_performance_problem.html

At the instant of your observation.

Re: Firefox freezing after upgrade to 146.0

Vincent — Mon, 29 Dec 2025 14:18:20 GMT

If this is happening on MacOS and you have an external monitor, you are likely running into this bug, that is on track for being fixed in the next release: https://bugzilla.mozilla.org/show_bug.cgi?id=1985140

Re: Firefox freezing after upgrade to 146.0

MPV — Mon, 29 Dec 2025 16:15:54 GMT

I am using an external monitor on MacOS. Thanks for your reply, I hope this is indeed fixed soon.

Re: Firefox freezing after upgrade to 146.0

vvz3n — Sun, 04 Jan 2026 01:29:04 GMT

Same behaviour here too on Linux 6.17.9-76061709. Running Firefox 146.0 on Pop!OS (Cosmic DE) on the main monitor of my workstation. The previous version was definitely not as crashy. I'd love to give more help for troubleshooting because this latest update has basically made Firefox unusable: it constantly crashes and it's almost always unresponsive after I log out and in again, forcing me to close it (and then even the crash handler seems to hang for a while, which forces me to `kill` it)

Re: Firefox freezing after upgrade to 146.0

forrie — Sat, 17 Jan 2026 04:39:36 GMT

To try and narrow this down (as best I can), I ensured my extensions were minimal, restarted Firefox, same issues. Then, I loaded up Brave Browser (chrome) and while the same Extensions aren't available, I created a similar environment. It was much faster, snappier.

I am used to Firefox, the API, the environment etc. But, something has changed recently that has slowed it down considerably, where it's akin to dialup modem performance at times. This is just unacceptable in today's terms of UX.

I implore Mozilla to invest more time in refining Firefox to be fast, efficient, performant.

Re: Firefox freezing after upgrade to 146.0

forrie — Sun, 01 Feb 2026 06:37:41 GMT

I've been able to observe the Webextensions process taking up CPU. At times, with Activity Monitor (MacOS), if I kill that process, things go better.

Using about:processes doesn't show individual extensions, so it's not clear to me which one may be problematic.

Is there a way I can figure out which extension is creating problems? It may be more than one, too.

But there are other times where I see Firefox struggles at times, and it's never clear where the issue is (to me).

Re: Firefox freezing after upgrade to 146.0

forrie — Sun, 01 Feb 2026 20:47:33 GMT

OK, so with the help of AI, I was able to dig into this and determined that one extension, Port Authority, was creating problems. But the number of hoops I had to jump through to GET there is, in my opinion, unacceptable and really unnecessary in this situation.

Why? I should be able to open about:processes and "expand" the Extensions to see which item was consuming resources -- this would have saved me a ton of time. It's great that we have profiling and technical data to drill down into, but for a situation like this, I feel this is completely unnecessary and, possibly, outside the reach of the average user.