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

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

You can first try to limit the number of content processes to 1.

• https://support.mozilla.org/en-US/kb/performance-settings

You may see three or more Firefox processes running.

• one process for the main Firefox thread (user interface)
• one or more content processes set via dom.ipc.processCount
  Options/Preferences -> General -> Performance
  remove checkmark: [ ] "Use recommended performance settings"
• one process for the compositor thread (Windows;graphics)

You can find the current multi-process state on the Troubleshooting Information (about:support) page.

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