Open Bug 2059903 Opened 2 months ago Updated 9 hours ago

Firefox feels slower than Chromium-based browsers, especially on GitHub

Categories

(Firefox :: Performance, defect, P3)

Product:
Firefox
Component:
Performance
Version:
Firefox 153
Type:
defect

Tracking

()

Status:
UNCONFIRMED

People

(Reporter: jehadhusein33, Unassigned)

References

Details

Firefox version: Latest stable

I've noticed that Firefox has become less responsive during everyday browsing.

The issue is most noticeable on GitHub. Opening repositories, issues, pull requests, and navigating between pages feels noticeably slower than Brave or other Chromium-based browsers on the same device and the same network.

My internet connection is stable, and I can reproduce the difference consistently. GitHub is the easiest place to notice it, although Firefox also feels less responsive on some other modern websites.

Expected result:
Firefox should provide smoother and more responsive page navigation comparable to Chromium-based browsers.

Actual result:
Page navigation feels slower, especially on GitHub.

Can you provide a performance profile using the Firefox profiler? Some details about what operations on github feel slower (and some sense of how much slower) would also be helpful.

I'm also curious if the same problem reproduces on a clean profile ( https://support.mozilla.org/en-US/kb/profile-management ), or if you've got more details on when things became slower, given you wrote:

I've noticed that Firefox has become less responsive during everyday browsing.

(emphasis mine)

If the issue reproduces on a clean profile, then a check with https://mozilla.github.io/mozregression/ could help narrow down when things slowed down.

From a quick check on just clicking around, I don't seem to be able to reproduce any meaningful performance difference. That isn't to say it doesn't exist for you - far from it - but to say we will need more details in order to figure out why it is slower on your machine.

Flags: needinfo?(jehadhusein33)

Redirect a needinfo that is pending on an inactive user to the triage owner.
:mconley, since the bug has recent activity, could you have a look please?

For more information, please visit BugBot documentation.

Flags: needinfo?(jehadhusein33) → needinfo?(mconley)

redirecting the needinfo back to the bug reporter and setting a low priority while we wait for more details

Severity: -- → S3
Flags: needinfo?(mconley) → needinfo?(jehadhusein33)
Priority: -- → P5

Hi, I am facing the same issue. Github is loading forever. Sometimes going back load the page. But it is also a hit and miss. Here is the profile I created hopefully it does not contains any secrets.
https://profiler.firefox.com/public/74gqrcq8zzk6sh8q055r4ej4fxqvf6sy6xbg5s0

Redirect a needinfo that is pending on an inactive user to the triage owner.
:mconley, since the bug has recent activity, could you have a look please?

For more information, please visit BugBot documentation.

Flags: needinfo?(jehadhusein33) → needinfo?(mconley)

(In reply to kcahtoor from comment #4)

Hi, I am facing the same issue. Github is loading forever. Sometimes going back load the page. But it is also a hit and miss. Here is the profile I created hopefully it does not contains any secrets.
https://profiler.firefox.com/public/74gqrcq8zzk6sh8q055r4ej4fxqvf6sy6xbg5s0

Thank you for sharing the profile.
I do see that it looks like we're waiting 800ms for a response from the github.com servers in this case.

Are you able to capture another profile with a slow navigation, this time using the "Networking" Firefox Profiler settings?

I am sorry. But I have to delete cache of Firefox to keep it using. I cannot reproduce it.

(In reply to kcahtoor from comment #7)

I am sorry. But I have to delete cache of Firefox to keep it using. I cannot reproduce it.

I appreciate you trying. We're working on reproducing it on our side as well.

I observed the issue on x86_64 / Linux / Arch / Wayland / Gnome / Nightly Desktop. Here's the profile: https://share.firefox.dev/4ydEMm4

See Also: → https://share.firefox.dev/4ydEMm4

Same on x86_64 / Linux / Ubuntu 26.04 / Wayland / Sway / Nightly Desktop 158.0a1 (2026-09-20): https://share.firefox.dev/3VbxVLt

Same on my Mac. See the discussion on https://connect.mozilla.org/t5/discussions/firefox-feels-slower-overall-especially-on-github/m-p/141957/emcs_t/S2h8ZW1haWx8dG9waWNfc3Vic2NyaXB0aW9ufE1VWFpGRkQzUVFZTDQzfDE0MTk1N3xTVUJTQ1JJUFRJT05TfGhL#M57997

It's slower after hours of usage, a coming back to an already opened github tab freeze for seconds (5 to 10).
Same without plugins.
My profiler: https://profiler.firefox.com/public/qg9rnjdgm3hn0201xfmhcvgysysq9n8n7ey4be0/calltree/?globalTrackOrder=x20x0nx17j9roq6haut1ve8lbg35dpsmikc2f4&hiddenGlobalTracks=1wmowqswv&hiddenLocalTracksByPid=2005-0w4~41424-0~2545-0~59500-0~2535-0~63950-0~20331-0~2543-0~82507-0~2569-01~23110-0~41433-0~2583-0~66395-0~2551-0~2688-0~2568-0~2563-0~93354-0~2565-01~93355-0~82506-0~93353-0~68751-01~41427-01~85947-0w2~2567-0w3~2534-02~75759-0w3~59489-0w2~20297-0w4~20326-0w4~20325-0w5&range=22006m6118&thread=xs&v=17

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:

Hey acreskey - some fresh profiles here. Any insights / anything actionable on our side?

Flags: needinfo?(mconley) → needinfo?(acreskey)

Hi, I came across this bug. Github has been literally unusable for very since 153. I'm on linux fedora KDE.
Another profile here: Github slow profiler

Andrew, any thoughts on these profiles?
macOS comment 11,
https://share.firefox.dev/3TLgIrK

Linux comment 13
https://share.firefox.dev/4iczmSP

Both spend almost all of active samples in CC.

What would be useful to capture next?

Flags: needinfo?(acreskey) → needinfo?(continuation)
Priority: P5 → P3

I don't yet have a good understanding of how frequently folks are bumping into this issue.

The Performance Impact Calculator has determined this bug's performance impact to be medium. If you'd like to request re-triage, you can reset the Performance Impact flag to "?" or needinfo the triage sheriff.

Platforms: [x] macOS [x] Linux
Impact on site: Causes noticeable jank
Page load impact: Some

Severity: S3 → S2

Hmm that's usually a sign that you are leaking DOM windows, which causes the CC optimizations to fail and then it is very slow. You could see evidence of that by looking for ghost-window entries in about:memory. Still hard to address without better steps to reproduce. It could be an addon doing something or something specific the user is doing.

Flags: needinfo?(continuation)

Hi can see the same behavior in a private browser after few hours of use.
My usage is to go to https://github.com/notifications then use the list to review the changes and use 'done' to return to the list. This tab is open for a long time.
Reloading the page doesn't change the behavior. I need to restart a new window.

I started having the same slowdowns since Firefox 150 series. Temporary relief is just to close Firefox completely, close the window, reopen the pages and it works fine for maybe half a day or a day, but then any longer sessions that are open slow to a crawl. And this is with maybe 10, 15 tabs in total, out of which GitHub is maybe two or three. So nothing crazy.

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