In current Firefox releases is multi-process tabs enabled. This means that see more than one Firefox process running, one process for the main browser process and processes for content processes (set via dom.ipc.processCount). See the "Help -> Troubleshooting Information" page under Application Basics: Multiprocess Windows. You may also see plugin-container processes for Flash. https://www.ghacks.net/2016/07/22/multi-process-firefox/ https://arstechnica.com/information-technology/2017/06/firefox-multiple-content-processes/ If instances are not running insane amounts of memory then it should be running properly Please let us know if this solved your issue or if need further assistance.