why is Firefox 140.0.2 so slow to open websites and to start up.

Here is the add-on I'm using to show load time. https://addons.mozilla.org/en-US/firefox/addon/load-time/?utm_source=addons.mozilla.org&utm_medium=referral&utm_content=search The screenshot shows the load time for Lexus in Japan. Show the issue by providing similar screenshots. If you're running Windows Pro version, I would test in the Sandbox to confirm. https://www.howtogeek.com/399290/how-to-use-windows-10s-new-sandbox-to-safely-test-apps/ Did you try with Firefox in Troubleshoot Mode? https://support.mozilla.org/en-US/kb/diagnose-firefox-issues-using-troubleshoot-mode#search Did you clear your browser cache? https://support.mozilla.org/en-US/kb/clear-cookies-and-site-data-firefox Try this dns tool to see if your current provider is part of the issue. https://www.grc.com/dns/benchmark.htm