Hello https://support.mozilla.org/en-US/questions/1550474 You can try. Task Manager - see whether tabs or extensions are slowing down. https://support.mozilla.org/en-US/kb/task-manager-tabs-or-extensions-are-slowing-firefox Firefox Profiler. https://profiler.firefox.com And, for information. https://support.mozilla.org/en-US/kb/use-troubleshooting-information-page-fix-firefox <blockquote>Multiprocess Windows: This shows you the number of Multiprocess Firefox windows (if any) and the total number of windows that are open. </blockquote> Multiprocess Windows 2/2 = 2 windows Multiprocess WIndows 3/3 = 3 windows And so on ...

Info on what you're seeing in task manager. Introducing Firefox’s new Site Isolation Security Architecture https://hacks.mozilla.org/2021/05/introducing-firefox-new-site-isolation-security-architecture/ You can try Firefox's Site Isolation feature Fission in Nightly now https://www.ghacks.net/2020/09/20/you-can-try-firefoxs-site-isolation-feature-fission-in-nightly-now/ Firefox's Project Fission: better security and more processes https://www.ghacks.net/2019/02/07/firefoxs-project-fission-better-security-and-more-processes/ Change how many processes multi-process Firefox uses: see screenshot https://www.ghacks.net/2016/02/15/change-how-many-processes-multi-process-firefox-uses/