Start Firefox in Troubleshoot Mode to check if one of the extensions ("3-bar" menu button or Tools -> Add-ons -> Extensions) or if hardware acceleration or if userChrome.css/userContent.css is causing the problem.

• switch to the Default System theme: "3-bar" menu button or Tools -> Add-ons -> Themes
• do NOT click the "Refresh Firefox" button on the Troubleshoot Mode start window

• https://support.mozilla.org/en-US/kb/diagnose-firefox-issues-using-troubleshoot-mode
• https://support.mozilla.org/en-US/kb/troubleshoot-extensions-themes-to-fix-problems

Boot the computer into Windows Safe Mode with network support to see if that has effect.

• https://www.bleepingcomputer.com/tuto.../how-to-start-windows-in-safe-mode/
• https://www.digitalcitizen.life/4-ways-boot-safe-mode-windows-10/

I'm using Firefox on Windows 11. Copy and paste in Firefox on Window 11 stops working

How about providing better detail on what exactly you're doing.

Hi jonzn4SUSE,

I'm just using Firefox as anyone might: Using Google and DuckDuckGo to search for and navigate to run-of-mill sites. Nothing special or out of the ordinary. Do not have any extensions installed. Unfortunately, I have seen no pattern to this.

When it breaks, copy-and-paste does not work when copying the URL, nor does it work copying content from a website.

After rebooting my machine, it works for a while, and then all of the sudden it doesn't. Wish I could give me info. Mostly curious to see if anyone else is seeing this symptom.

I suppose I could try to copy-and-paste after every page I open to see if there's some sort of rhyme or reason.

Thanks for the update. What version of Windows? If Pro, can you fire up Windows Sandbox and see if you have the same issues in the VM? https://www.howtogeek.com/399290/how-to-use-windows-10s-new-sandbox-to-safely-test-apps/

Also, how about using OBS or sharex to screen record and post to YouTube and then provide us a link to see the issue. What security software are you running?

Does it still happen in a new profile? An easy way to test a new profile is to install Developer Edition and see if it happens there or refresh your existing profile. Make sure you stay signed out of your sync account when testing.

This morning, after the computer was in sleep mode all night, the copy-and-paste did not work. I'll follow this clue to see if it leads anywhere.