Hi chl_1959, Firefox opens a certain number of content processes and shares them between your open tabs. There is not a one-to-one correspondence, although that might happen in the future. I personally never close enough tabs to know what happens when I go below 15 to 20, but others may be able to compare their experience. Anyway, if you would like Firefox to use fewer content processes, you can modify the settings as described in the following article: [[Firefox's performance settings]]. Does it make any difference? Also: [[Quick fixes if your Firefox slows down]]. And finally, some malware may disguise its traffic using Firefox processes. If you are not actively browsing but you notice some Firefox processes using a lot of resources, and especially if you close all visible Firefox windows but some processes do not shut down within 30-60 seconds, try some scans: [[Troubleshoot Firefox issues caused by malware]].