More than one process is normal for the current Firefox. http://www.ghacks.net/2016/07/22/multi-process-firefox/

Multi-process Firefox is codenamed "e10s". https://wiki.mozilla.org/Firefox/multiprocess

Try to disable multi-process tabs in Firefox. You can disable multi-process tabs in Firefox by setting the related prefs to false on the about:config page.

browser.tabs.remote.autostart = false browser.tabs.remote.autostart.2 = false

http://www.ghacks.net/2016/07/22/multi-process-firefox/

Type about:config<enter> in the address bar. If a warning screen comes up, press the Be Careful button. At the top of the screen is a search bar.

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/