I switched to Kubuntu 25.10 on my desktop from Windows 10 and every since, I’ve noticed that Linux on my primary monitor has felt very choppy with a low FPS. Animations are choppy and slow. As soon as I drag it to my second monitor, everything is faster and has higher FPS. This doesn’t happen on Windows. testufo.com shows ~20fps on the problematic monitor I also haven’t noticed this behavior with any other programs. There are spikes to 50fps and smoother animations when I open the Firefox menu, but then it goes back to 20fps. Chromium on the same monitor is faster and shows 50+fps. Games on this monitor also are higher fps
The primary monitor is configured to 60Hz, the second monitor is 143.97Hz. I’ve got an Nvidia GeForce 2070 with the NVIDIA driver (open kernel) metapackage from nvidia-driver-580-open installed, 32GB of RAM, plenty of CPU, and no other programs or tabs open even.
What could cause this issue and how can I fix it?
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The slow monitor is plugged into the graphics card, not the motherboard, right?
Yep, both are plugged into the graphics card. Other programs and games are a lot faster.
I recall this happening on my higher refreshrate and resolution screen on X11 and nvidia (iirc a 2070 super). Moving to wayland fixed it.
I mainly noticed frame drops in videos in forefox, but I’m sure scrolling was also affected.It probably manifests on a per usecase basis since it depends on how exactly the gpu or x11 is loaded. Whatever it is, it’s some consequence of x11 being flawed at its core abd just not scaling well with modern usecases.
In my case I was forced onto wayland after I got my new better monitor due to how choppy x11 felt.
I had 2 1080p 60Hz and got a 4k 120/144Hz screen.Interesting. I played around with X11 vs Wayland settings just to see what different configurations give me
MOZ_ENABLE_WAYLAND=1 /snap/bin/firefox- Exhibits low FPS issueMOZ_ENABLE_WAYLAND=0 DISABLE_WAYLAND=1 /snap/bin/firefox- Actually feels fast like it should be. Most animations feel faster, some are still choppy though. It’s hard to tell.
It seems like running with X11 sort of the problem? Which seems unexpected and concerns me since I know distros are starting to default to Wayland.
Check if you have hardware acceleration enabled for Firefox. It’s usually disabled OOTB for some reason.
I had the exact issue. My monitors were different resolutions, so I scaled my 4k display so it matched my 1440p monitor which was like a 175% increase. Linux doesn’t seem to like fractional scaling, and it worked normally when scaling was set to 200%.
YouTube videos were still choppy though. Turns out the ambient mode on videos was causing that
Fractional scaling is a compositor issue, not a linux issue, so in this case kwin. But yes, fractional scaling in general is always problematic as there’s no way to cleanly multiply pixels by fractions, so you get wonky fonts, UI that doesn’t quite fit… and whatever hacks your compositor has on top to make it look better, it’s best to avoid it if possible and only increase the font size.
Disable Hardware Acceleration
