I have Firefox 76.0.1, Sandboxie 5.33.3, Win 10 Pro 1909 TEST SETUP Open FF non-sandboxed. Open a new tab. Close any other tabs. Close FF. So, the next time FF opens, there's only one new tab. Open FF non-sandboxed in one browser. Open FF sandboxed in a second browser. Do a google search in one browser, for example "firefox sandboxie high cpu". Duplicate that tab twice, giving 3 identical tabs. Do the same 3 tabs in the other browser. So, the taskbar shows only 2 Firefox and Task Manager. There will be other background processes, such as Win Defender, MBAM, reminders. TEST RESULTS For the non-SB browser: CPU = 0.2% For the SB browser: CPU = 33% Info: My feeling is that FF+SB can run for a long time on a CPU of 1%, as long as there's no google search results in a tab (I'm referring to the list of hits - with none of these hits being opened). As soon as a google search is done, the CPU can jump to 100% then settle down at ~33% Thanks.