Firefox feels slower overall, especially on GitHub

[jehad]

I've been using Firefox on Android for a long time, and I'm currently on the latest version. Lately, it feels less responsive than it used to during everyday browsing.

The slowdown is most noticeable on GitHub. Opening repositories, issues, pull requests, or simply moving from one page to another often takes longer than expected. My internet connection is stable, and when I compare the same tasks on Brave or other Chromium-based browsers on the same device, they generally feel smoother and faster.

I've also heard similar feedback from a few people who stopped using Firefox. Their main reason wasn't missing features—it was performance.

I really like Firefox and would prefer to keep using it, so I'm sharing this in case others are seeing the same thing. Is this a known issue, or are there any plans to improve performance on modern websites like GitHub?

[chrcoluk]

I have observed the same issue, but for me it started after updating to 157, loading any github page causes a delayed CPU surge 3-5 seconds after page loaded, which is on the main FF process, stalls scrolling etc.  githubassets scripts are the culprit, if they are disabled, the CPU surge doesnt happen, but of course the site doesnt function properly either with them disabled.

I agree with you fixing compatibility and performance should always take priority over things like AI features and UI changes.

[zaneselvans]

I'm also having constant 3-5 second freezes on GitHub, seemingly no matter what page I'm on, and every 10 seconds or so, which makes writing anything or interacting with the UI very difficult.

[kerny]

Same on my side since the update yesterday (v157). It was slow before but there is a huge gap, I can't accept for my daily work on github.

When I switch to another application and come back on an opened PR, the full page is displayed blank and freeze for 5+ seconds. When typing a comment on a PR there are freeze of several seconds where I can't see the char I typed.

If its' not addressed, I will definitely move to another browser.

[dftf]

@kerny : if you try GitHub in Menu -> Help and Report -> Troubleshoot Mode... , do you still get the same speed issues then?

If not, an extension you use will likely be causing the issue.  Script/ad-blockers (e.g. AdGuard, Ghostery, NoScript, uBO) or page-themers (e.g. Dark Reader) would be the most-likely causes.

[kerny]

Hi,

I removed my extension and restart FF. It works fine.

But 24h later, it's slower and  slower. The same troubles reappear:

• Every is slower on github, like switching form 'Conversations' to 'Files changed' tabs.
• I have again freeze of seconds when typing a comment
• I have freeze of 5 to 10s when I return on a github ta (PR view). This is not always b ut quite often.

I think it hard to imagine it's related to my profile.

This is a capture of returning on tab that freeze.

At 22,120s I clicked on the tab to display it, it became blank until 27.2s (~5s). I can't understand why. I also do other test, there isn't network long requests at the same time.

I have 2 FF windows with ~20 tabs. One of them have mostly tabs with github issues and PR.
Here is the captured profile:

https://profiler.firefox.com/public/qg9rnjdgm3hn0201xfmhcvgysysq9n8n7ey4be0/calltree/?globalTrackOrd... 

[dftf]

See if any of these tickets on BugZilla may be relevant, and you could perhaps add your own comments and profile tracer to them:

Desktop Firefox:

https://bugzilla.mozilla.org/show_bug.cgi?id=2059903 

Android Firefox:

https://bugzilla.mozilla.org/show_bug.cgi?id=2060501 

[dftf]

Odd how many people are suddenly having issues on GitHub, when I've used it at-least twice to report issues since the 157.0 release and haven't noticed any.  (Admittedly browsing Issues and filing one won't be the most CPU-intensive thing you could do on there.)

For those who are, can you try:
1. running GitHub in a "Private Window", where by-default no extensions should run; or
2. run Firefox in Troubleshooting Mode (Menu -> Help and Report -> Troubleshoot Mode)

In Troubleshoot Mode, no extensions or custom themes run, and all your settings get ignored.  If GitHub works fine there, it's likely an extension causing the issue in your normal mode.  If you use ad-blocker, script-blocker, tracker-blocker or extensions that theme pages (e.g. Dark Reader), try turning them off while on GitHub and see if you can identify the one causing the issue.

You can also see if anyone else has reported a GitHub issue here:
https://bugzilla.mozilla.org/buglist.cgi?quicksearch=github 

I'm not seeing any reports of GitHub issues in r/Firefox at this time.

[chrcoluk]

I think this would be reasonable if the issues didnt suddenly start after a major browser update.

Troubleshooting extensions when the only change in the browser is the build number seems a wild goose chase, but regardless I already have done troubleshooting mode before I posted my first comment and it had no effect.

I can also confirm downgrading to 156 fixed the issue, with the exact same extensions.

However like one of the commenters said, the performance on github on 156 isnt clean, it seems it also spike on that, but the difference is the spike is considerably lower, and there is no block on scrolling etc.

Finally there is a large thread on firefox sub reddit reporting a github issue, and a smaller thread a few days before that.

As kerny said, its not a minor issue, the site becomes very painful to use, its the kind of issue that makes people switch browsers.  These type of issues should be the top priority for investigating and fixing. I myself will be uploading a performance trace to try and help get this diagnosed.

[dftf]

It looks like there is an official BugZilla ticket for it you can refer to, and add to:

https://bugzilla.mozilla.org/show_bug.cgi?id=2059903 

There's also a separate one for the Android version of Firefox here:

https://bugzilla.mozilla.org/show_bug.cgi?id=2060501 

[kerny]

will do another test with a long usage in a private window.

[chrcoluk]

Further evidence its a problem.

https://github.com/orgs/community/discussions/27334

[EmmaCollins765]

I agree that Firefox’s performance on websites like GitHub could be improved. Keeping the browser updated to the  may help with performance fixes, compatibility, and a smoother browsing experience. Hopefully, future updates will make navigation faster and more responsive on Android devices.

[zarkoa]

Same issue, GitHub has become barely usable in Firefox 150 series. Closing the window completely helps temporarily but as soon as you have a longer session GitHub pages slow to crawl.