Try referring to this thread; https://support.mozilla.org/en-US/questions/1147868

Well said, Zachary_

Thank you Zachary for this response. I did verify that e10 is turned on with Multiprocess Windows set at 1/1 (default). I will monitor usage level to see if this is higher than when multiprocess is not running and if necessary the link you provided had easy to understand information on how to reset. Thanks for your help.

You may see three or more Firefox processes running.

• one process for the main Firefox thread (user interface)
• one or more processes for content threads set via "Options/Preferences -> General -> Performance" (dom.ipc.processCount)
• one process for the compositor thread (Windows)

You can look at "Multiprocess Windows" to see the current multi-process state.

• "Help -> Troubleshooting Information" -> Application Basics: Multiprocess Windows

See also:

• https://www.ghacks.net/2016/07/22/multi-process-firefox/
• https://www.ghacks.net/2016/11/11/firefox-52-nightly-quantum-compositor-has-landed/
• https://hacks.mozilla.org/2017/04/firefox-53-quantum-compositor-compact-themes-css-masks-and-more/

There option to limit one process does not work with the new Firefox Quantum so you will have to use and older version of Firefox and then it may actually work.

This does not work in the newest version of Firefox and will NOT run only one process. I am a 35 year computer tech with a LOT of experience. Firefox will need to patch the new Firefox Quantum to allow this option to work.