See: *https://support.mozilla.org/en-US/kb/quick-fixes-if-your-firefox-slows-down *https://support.mozilla.org/en-US/kb/firefox-uses-too-much-memory-or-cpu-resources ----- Start Firefox in <u>Safe Mode</u> to check if one of the extensions ("3-bar" menu button or Tools -> Add-ons -> Extensions) or if <u>hardware acceleration</u> is causing the problem. *switch to the DEFAULT theme: "3-bar" menu button or Tools -> Add-ons -> Themes *do NOT click the "Refresh Firefox" button on the Safe Mode start window *https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-using-safe-mode *https://support.mozilla.org/en-US/kb/troubleshoot-extensions-themes-to-fix-problems Boot the computer in Windows Safe mode with network support to see if that has effect in case security software is causing problems. *https://www.bleepingcomputer.com/tutorials/how-to-start-windows-in-safe-mode/ *https://www.7tutorials.com/4-ways-boot-safe-mode-windows-10