Firefox normally reserves content windows, so they are ready to be used if you open more tabs. It is quite normal to see more Firefox processes running. *process for the main Firefox thread (user interface) *one or more content processes<br>you see more content processes when Fission is enabled *process for the compositor thread *process for extensions *process for WebRender when this feature is enabled There are several toolkit.aboutProcesses prefs on the <b>about:config</b> page to show more info. You can find the current multi-process state on the Troubleshooting Information page (about:support). *"Help -> Troubleshooting Information"<br>"Application Basics":<be>Multiprocess Windows and Fission Windows<br>"Remote Processes" (Web Content) You can check the <b>about:memory</b> and <b>about:processes</b> pages for info about all processes. See also the <b>about:unloads</b> page for info about the tabs.