Firefox 136.0.3 is ridiculously slow even in Safe Mode

[Graham_M]

Earlier today I upgraded to Firefox 136.0.3 64 bit with Windows 10 and now, even in Safe Mode, it's extremely slow to load pages, if at all.

If I run it in normal mode with NoScript, uBlock and various other add-ons active, it is effectively unusable because pages simply will not load, just sit there with the hourglass on the tab.

I tried to downgrade to the previous version, but it's telling me that my profile is from a later version, so I need to create a new one.

Anyone got any ideas how to fix this as I'm having to post this in Chrome because I can't even Log In here using Firefox!

[Graham_M]

 ADDENDUM: I found the Firefox Task Manager and restarted in Normal mode.

I've got it trying to use 140% of CPU!

[siffemcon]

You could file a bug:

- via the address bar, go to about:config > click 'Copy text to clipboard' > paste to a text file and save it

- via the address bar, go to about:memory > click 'Measure and save'

- file the bug at https://bugzilla.mozilla.org/enter_bug.cgi?format=guided.

- click the 'Attach New File' button to upload your two saved files

[Windows_Vista]

The experience you described with Firefox 136.0.3 is incredibly frustrating and it highlights an ongoing issue with Firefox’s performance. Having the browser use 140 percent of your CPU even in Safe Mode is not acceptable. These kinds of problems are not just a minor inconvenience, they are a signal that something fundamental needs to change. Hmm weird, I have no problems like you did even on Firefox 136.0.3, my Firefox install is totally fine, but still, I want to spearhead the idea to rebuild Firefox.

This is where a complete rebuild of Firefox with a new engine like Servo could make all the difference. Gecko has served its purpose but it is clear that it is struggling to keep up with modern demands. Servo, being a modern high performance engine, is designed to provide a faster smoother browsing experience while also being more efficient in resource usage. It is exactly what Firefox needs to remain competitive and address the kind of performance issues you and many others are facing.

Mozilla should prioritize investing in Servo and making it the backbone of Firefox. This would not only solve many of the performance problems tied to Gecko but also position Firefox as a true competitor in the browser market. I recently started a discussion advocating for Mozilla to retire Gecko and fully commit to Servo. You can check it out here https://connect.mozilla.org/t5/discussions/when-is-mozilla-gonna-ditch-the-gecko-browser-engine-for-...

We need to push Mozilla to focus on the changes that truly matter. A modern efficient browser engine like Servo could be the solution to the issues you are experiencing and the key to making Firefox great again.

[michaelr198]

I also am experiencing slowness since the last update and running the newest version of Windows 11.

[Graham_M]

It seems to have improved slightly after I upgraded again, this time to 136.0.4, but it's still sluggish at times.

I'll try filing a report and see if that gets any report. 

[ErikS]

Same problem here. Several sites (including my bank's) load incredibly slow and have become almost unworkable. And still no solution!

[Graham_M]

Upgrading to 137.0 seems to have made things a bit better, maybe that will help you?

[ErikS]

Yes, just al tiny little bit. Problems still occur! Even the update to 307.01 does not solve the problem!
When will, there be a final solution! Or do I just have to say "Goodbye Mozilla Firefox"

[Windows_Vista]

Mozilla is just terrible but I'm not a fan of Chromium based browsers like Manifest v3 stinks maybe we try Orion browser (which can use both Firefox and Chrome extensions), plus its not based on M0ZiLl@ FiR3fOx or ChR0m3 which both browsers are **bleep** for different reasons. I cannot wait until we have LadyBird Browser.

[BigBubbler]

This covers my experience since the new update(s):

"extremely slow to load pages, if at all."

Important tab took me 25 minutes to get it to load. Happening across many different websites, so definitely seems Firefox is "damaged goods" at this time.

[ErikS]

I've been doing some experimenting and come up with the following;
If I start Firefox in troubleshooting mode it works again as normal. If I then restart again I have the problem again. The difference is that in troubleshooting mode, all extensions are disabled.
Then I manually disabled all extensions and now Firefox also works normally. So it is in one or more installed extensions.
Now only to find out which ones are causing the slowdown.
When I figure it out I will report back!