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Using backdrop-filter: blur in Firefox when no GPU acceleration is available makes things extremely laggy. One common case where this happens is when running Firefox in a remote desktop session. Backdrop-filter blur works well without GPU acceleration on Chromium 140. Issue seen on both Firefox ESR 128 on Red Hat Enterprise Linux 9 and in Firefox 142 on Fedora 42. These are the packaged Firefox versions installed via DNF. Reproducible: Always Steps to Reproduce: 1. Open Firefox in a remote desktop session without GPU acceleration. 2. Open the attached HTML file. 3. Scroll to see the problem. Actual Results: Scrolling on the website is very, very slow. Expected Results: The blur property should work well, even on CPU fallback. By disabling backdrop-filter in the web inspector, you can see that things start working normally again. Additional Information: Also reported to Firefox: https://bugzilla.mozilla.org/show_bug.cgi?id=1988728 I cannot reproduce the issue on Fedora 42 with the nightly build of Firefox downloaded directly from Mozilla. Could this be an issue with Red Hat's Firefox builds?
Created attachment 2106787 [details] HTML file that shows the problem
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Fedora Linux 42 entered end-of-life (EOL) status on 2026-05-27. Fedora Linux 42 is no longer maintained, which means that it will not receive any further security or bug fix updates. As a result we are closing this bug. If you can reproduce this bug against a currently maintained version of Fedora Linux please feel free to reopen this bug against that version. Note that the version field may be hidden. Click the "Show advanced fields" button if you do not see the version field. If you are unable to reopen this bug, please file a new report against an active release. Thank you for reporting this bug and we are sorry it could not be fixed.