User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:109.0) Gecko/20100101 Firefox/112.0

Steps to reproduce:

Many programs have difficulties synchronizing different refresh rates across multiple monitors. Firefox is no exemption here, but since this is handled way better in chromium based browsers and there is a workaround, this should be able to be improved.

To make this issue easily visible, open the following website
https://www.testufo.com/animation-time-graph

This graph shows the smoothness of the browsers performance but the results will not show the actual problem here and are NOT important. Wait until the performance is steady and then look closely at the movement of this graph. As the graph moves, the green bar will start to flicker if performance is suboptimal. Using a 144hz and a 270hz monitor there will be very obvious flicker. This is not the case in chromium based browsers.

A workaround to stop the flickering and therefore the microstutters is to set both displays to the same refresh rate, after that restart Firefox and then the flicker will be gone. Now even after changing the refresh rates back to different ones, as long as Firefox wont be closed, the stuttering will still be fixed and not noticeable.

Actual results:

When browsing the web, especially when scrolling, stuttery movements are noticeable.

Expected results:

Movements should be smooth, even when 2 monitors are connected with different refresh rates.

The Bugbug bot thinks this bug should belong to the 'Core::Performance' component, and is moving the bug to that component. Please correct in case you think the bot is wrong.

This bug was moved into the Performance component.

:pasi123567, could you make sure the following information is on this bug?

• For slowness or high CPU usage, capture a profile with http://profiler.firefox.com/, upload it and share the link here.
• For memory usage issues, capture a memory dump from about:memory and attach it to this bug.
• Troubleshooting information: Go to about:support, click "Copy raw data to clipboard", paste it into a file, save it, and attach the file here.

If the requested information is already in the bug, please confirm it is recent.

Thank you.

This bug was moved into the Performance component.

:pasi123567, could you make sure the following information is on this bug?

• For slowness or high CPU usage, capture a profile with http://profiler.firefox.com/, upload it and share the link here.
• For memory usage issues, capture a memory dump from about:memory and attach it to this bug.
• Troubleshooting information: Go to about:support, click "Copy raw data to clipboard", paste it into a file, save it, and attach the file here.

If the requested information is already in the bug, please confirm it is recent.

Thank you.

FF Profile stutter: https://share.firefox.dev/3G5Vmvp
FF Profile workaround (no stutter): https://share.firefox.dev/3lRbpq3

about:support data stutter: https://pastebin.com/nGgLPnAx
about:support data workaround: https://pastebin.com/BrwNUFD4

This bug was moved into the Performance component.

:pasi123567, could you make sure the following information is on this bug?

• ✅ For slowness or high CPU usage, capture a profile with http://profiler.firefox.com/, upload it and share the link here.
• For memory usage issues, capture a memory dump from about:memory and attach it to this bug.
• Troubleshooting information: Go to about:support, click "Copy raw data to clipboard", paste it into a file, save it, and attach the file here.

If the requested information is already in the bug, please confirm it is recent.

Thank you.

Still hoping for a response. I feel like this is an easy issue to fix to make Firefox much more smooth for multiple display setups.

This is a graphics issue, moving to the appropriate component.

The severity field is not set for this bug.
:bhood, could you have a look please?

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