MacBook Air, YouTube freeze, cursor visible but does not operate

Try the following

1. Force quit Firefox: Press Command + Option + Esc simultaneously. In the Force Quit Applications window, select Firefox and click Force Quit.
2. If force quitting doesn't work, try a hard restart: Press and hold the power button for about 10 seconds until your Mac shuts down completely. Wait a few seconds, then press the power button again to restart.
3. If the issue persists after restarting, boot into Safe Mode.

If you can now regain access to your Mac's Desktop, I suggest a few more things:

1. Once you can access Firefox again, clear its cache and cookies.
2. Disable hardware acceleration in Firefox.
3. Update Firefox and macOS: Ensure both your browser and operating system are up to date, as this can often resolve compatibility issues.
4. Disable Firefox extensions one by one to see if any of them are causing the issue.

If none of the above helps, your next step will be to contact Apple Support directly for further assistance with this matter. To do so, simply select the "Support" link on the lower left-hand side of this forum's web page.