Always curious to see what users are working with when reporting this issue. Post a screenshot of the performance tab from task manager.

Firefox's Project Fission:

Introducing Firefox’s new Site Isolation Security Architecture https://hacks.mozilla.org/2021/05/introducing-firefox-new-site-isolation-security-architecture/

Firefox's Project Fission: better security and more processes https://www.ghacks.net/2019/02/07/firefoxs-project-fission-better-security-and-more-processes/

Enable Fission in Firefox https://www.ghacks.net/2020/09/20/you-can-try-firefoxs-site-isolation-feature-fission-in-nightly-now/

Change how many processes multi-process Firefox uses https://www.ghacks.net/2016/02/15/change-how-many-processes-multi-process-firefox-uses/

Which performance meter would you like to see? There are 7...here is the CPU with Firefox open and 22 processes for this one tab open in browser, task manager and Outlook open. Also the Memory screenshot

And just for giggles I tried your suggested link and followed the instructions changing the number from 8 to 1 and now I have 30 processes going...not less same apps open with 3 tabs in browser https://www.ghacks.net/2016/02/15/change-how-many-processes-multi-process-firefox-uses/

Thanks for the screenshots Steph. If you look at my screenshot, you'll see the fission thingy. Tweak that also and see if it helps.

Just an FYI... see screenshot

Very sneaky there Jon- so you suggest upgrading my entire computer to run a web browser more efficiently? I run Revit Autodesk software just fine with this old clinker.... I looked at your screenshot about the "fission" search and mine says true- are you saying that is what it should say?

Not just for the browser, but for you.  ;-)) Try Fission 'False' and see if the number goes down. https://support.mozilla.org/en-US/kb/performance-settings?as=u&utm_source=inproduct