Firefox slow and clunky... should I switch browsers?

Hi all. Firefox has been my browser of choice for 15 years. However, I've noticed that it seems to be somewhat... slow and clunky. The youtube videos are all choppy for 15 seconds and the words don't match the mouth. This disappears immediately if you switch over to fullscreen. But if you go back to small screen, it's probably going to be choppy again. This may have something to do with the reason that some ads make it past Adblock Plus, on youtube. It's almost like things are loading in the wrong order... or something. I've never had this kind of trouble before, the ads have always been blocked when using Windows or Mac.

It also doesn't seem to like to load dark themes for sites right away. It usually flashes your eyes with a bright white screen first, and then loads all of the darker themes. In fact, most websites just don't load very smoothly. So I'm wondering if this is a firefox problem, and maybe I should just switch to Chromium or something like IceWeasel or Icecat or whatever it's name is these days. I know that's a firefox fork, but it could be that they do a better job with linux than Mozilla is doing these days.

Anyone else have this same kind of clunky, slow behavior out of firefox? System specs below:

Manjaro KDE
AMD RX 560
8Gb DDR3 1600
Samsung SSD
Intel DH67CF motherboard
Power supply from 2008 walmart computer

Use uBlock Origin


I am using Firefox - and it is better than ever.

Lately I have noticed a lot of topic on speed and responsiveness - and then trend seems to include KDE - that may - however - be due to the popularity of KDE - but nonetheless.

On a Firefox related note: I use only the build-in ad-blocking - in strict mode - and have enabled webrender.

Added DuckDuckGo for extra filtering.


I can not reproduce those issues.
I have to admit though, i don't understand this

It also doesn't seem to like to load dark themes for sites right away. It usually flashes your eyes with a bright white screen first, and then loads all of the darker themes

part at all.

I can second this. A bad add-on can really mess up your browser. Also, @bennylava if you really cannont fix it, try refreshing Firefox. Be aware this will delete your history, saved logins, add-ons, etc but it usually fixes the problem.

If you want to refresh, in Firefox, type about:support into your address bar and hit the refresh button. Again, make sure you backup/save important stuff. Or you can try safe mode to see if it is in fact, the add-ons causing your issue. My Firefox is working well.


[This reply should have been to bennylava. Newbie error.]

My experience with Firefox 74.0 is that it's better than ever.

I experience one small annoyance with YouTube: if I switch between windowed-mode and fullscreen while a video is playing, things can get funky like you described, with audio/video out of sync, etc. But as long as I remember to pause the video before switching display mode, it works great.


Yes. No. Maybe.

Blue. No, yel--


Try without your extensions .. as it seems you may be prone to using bad ones like ABP.
Or maybe its an underlying issue with your system configuration.
We wouldnt know without real system info ( How to provide good information in your posts )
And its pretty trivial for you to try out another browser - install falkon or chromium or... Then test it.


From what I read :

  • check your ISP box (is it updated ? restart it - apply the updating procedure)
  • show us your addon list :
grep -oP '},"name":"\K[^"]+' ~/.mozilla/firefox/*.*/addons.json
  • I confirm you have to get rid of Adblock plus & replace it with Ublock Origin
  • For the dark theme sites, give us examples - usually's if you see light then dark theme, it is bad css on the site or a ■■■■■■ dark theme extension on your browser.

You also may have memory management issues, give us :

cat /proc/sys/vm/swappiness
cat /proc/sys/vm/vfs_cache_pressure
swapon -s
free -h --si

Firefox can sometimes consume more CPU and RAM resources than Chromium on certain sites depending on how they are coded. I have seen this on my machines and I don't run any extensions in either so it's simple to compare the two. I enter competitions on a site called iWon. If you open enough tabs from this at the same time by clicking through to open tabs for all the competitions at once, you can max out a machine with 8GB of RAM in Firefox and of course it takes longer to do so. In chromium the total RAM consumed is around 6GB instead. That's a clear indication to me of the difference in ability to handle scripts between the two browser engines.

Whether you should switch is still your call though. There are multiple threads covering the pros and cons of each browser available on this forum already. Most boil down to privacy concerns though.

1 Like

Yeah I'm not sure why it does that either. If there's a site with a dark theme, typically firefox will show the original bright white theme first, then switch on the dark theme like it's supposed to. This can be somewhat... off putting at night. Any site that I frequent that has a dark theme, I'm using it. It doesn't always happen, but most of the time it does.

Here's the output from those commands that nam1962 recommended that I post up:

Matte Black (Red)
Dark Theme for Google™
Dark Theme for YouTube™
uBlock Origin

                  total        used        free    shared    buff/cache   available
Mem:               7.9G        3.0G        766M    687M      4.2G         4.0G
Swap:                0B          0B          0B

unfortunately it doesn't really line up but I think you can still tell where everything is supposed to go. 7.9G total memory. 3.0G free. 766M shared, 4.0G available. That's with 6 firefox tabs open and 2 of them are youtube videos, although they're not playing. I don't have the swap file turned on, i prefer not to use it if I don't need one.

U know the rule : ■■■■ in, ■■■■ out.
So... get rid of :

  • Pushbullet (I don't get the benefit, if U really want to use WhatsApp, use it through Hamsket... )
    Matte Black (Red)
    Dark Theme for Google™
    Dark Theme for YouTube™

I have no clues about MetaMask

Can U give us all asked commands returns?

We don't care about feelings about swap, but about facts.

1 Like

Note - I edited your output.
In the future you can enclose with 3 ticks (```) or you can use the </> code button.
Also - you have it twisted .. most of your RAM is being used by the cache/buffer.

1 Like

During last week, I've tried Firefox 76 nightly and Wayland. On sway, Gnome/Wayland and Plasma/Wayland.

76 Nightly now support h264 and vp9 hardware decoding on Wayland.

Result is quite amazing. Playing 4k@60Hz on YouTube flawlessly without maximum fan speed. Almost on par with mpv in case cpu consumption. UI responsiveness is much better. Smooth scroll is almost perfect.


But wayland is still not for prime time.

1 Like

Thank you for the reply. I don't think that I want to put the Cache on the RAM because it would wipe out all the site date each time. Sounds like a cool idea, but there's certain things I want to be saved. It is nice not to have to use a swap file though, although I'm wondering if I might actually need to upgrade to 16Gb of RAM for that these days.

Anyway I think that some of my addons may have been the trouble. As per one member's recommendation, I switched away from Adblock Plus and that seems to have sped things up some. I also got rid of the youtube dark theme addon when I remembered that youtube has one natively in the site.

As for sites that flash a bright white screen before loading the site in dark theme mode.. this site is one of them. Here's another site. Also note how long it takes to load this site:

Granted that isn't actually all that long, it's just longer than I'm used to waiting on that site. I use windows as a comparison (i know, for some strange reason that just makes linux fanboys scream while clawing their eyes out) and it does not flash the white screen first on either site, and it loads slower sites slightly faster. Who knows why. But again, it does seem to have at least sped up a bit since getting rid of those two addons.

We still need :

grep -oP '},"name":"\K[^"]+' ~/.mozilla/firefox/*.*/addons.json
cat /proc/sys/vm/swappiness
cat /proc/sys/vm/vfs_cache_pressure
swapon -s
free -h --si

Expressing opinions or feelings is nice, but wont help, data will help.

This overclock site is not designed for performance :stuck_out_tongue:

Well yes but again, I already fixed the issue by way of recommendations here. It must have been one of those addons that was causing the problem. Firefox does seem faster now.

Cool. Why not tagging it as solved then.

1 Like

Well, you felt it was slow, you now feel it seems faster and it must (may, perhaps..) be due to...

I'm always puzzled when an OP refuses to give command feedback.


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