You can set this pref to ''1'' in about:config to limit the number of content processes. *about:config => dom.ipc.processCount.webIsolated => 1 You can open <b>about:config</b> via the location/address bar. On the warning page, click "Accept the Risk and Continue" to open about:config. *https://support.mozilla.org/en-US/kb/about-config-editor-firefox ----- 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 You can find the current multi-process state on the Troubleshooting Information page (about:support). *"Help -> Troubleshooting Information"<br>"Application Basics":<br>Multiprocess Windows and Fission Windows<br>"Remote Processes" (Web Content)