Diminishing performance (increasing lag) the longer Firefox 133 is open
I believe this problem began in 133. I've noticed that if FF is open for a few hours, it starts to develop a very noticeable input lag. For example, if I'm watching a YouTube video and hit an arrow key to advance the video, there will be a couple of seconds before the browser registers the key press. It behaves like a high CPU issue but I do not detect high CPU usage when this is happening. Restarting the browser resolves the issue for a few hours.
This is happening on Windows 11 as well as on a Mac running Sonoma.
All Replies (5)
Have you tried Firefox in Troubleshoot Mode? https://support.mozilla.org/en-US/kb/diagnose-firefox-issues-using-troubleshoot-mode#w_how-to-start-firefox-in-4troubleshoot-modesf5safe-modesf
I haven't tried that yet. It usually takes a few hours before the problem appears and it's intermittent. It might take a while to see if it appears in Troubleshoot Mode.
Also, I'm not sure this is related, but after some time I also notice that it starts to become difficult to click on URL links. As with the other issue, restarting the browser clears it up. I believe both of these issues began in v133.
If Windows Pro version, try testing in Windows Sandbox (VM) to see if you have the same issue. https://www.howtogeek.com/399290/how-to-use-windows-10s-new-sandbox-to-safely-test-apps/ You can also boot windows to safe mode with networking to test.
Hi John, I've seen several threads over on Reddit about YouTube issues in Firefox 133. It may be related to higher-than-HD video (like 1440p), but because the slowdown comes on gradually, it is very difficult to backtrack what may have caused the problem. One user noted that opening videos in a new tab (you can right-click (Ctrl+click) > Open Link in New Tab, or Command+click the link) improved performance, especially if you closed the source tab.
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