Do you give Firefox enough memory to run properly as it is possible that Firefox runs out of memory? You may have to limit the number of tabs and possibly set <b>dom.ipc.processCount.webIsolated</b> to "1" in about:config. *https://support.mozilla.org/en-US/kb/about-config-editor-firefox 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) You can check the <b>about:memory</b> and <b>about:processes</b> pages for info about all processes. There are several <b>toolkit.aboutProcesses</b> prefs in <b>about:config</b> to show more info. See also the <b>about:unloads</b> page for info about the tabs. *https://Firefox-source-docs.mozilla.org/browser/tabunloader/