Firefox constant 25% cpu usage in SANDBOXIE

Question

Sandboxie 5.31.6 x64 on Windows 10 1909, FF 70.0.1 x64, similar issues I have reported previously in windows 7 and windows 10 1809. Firefox safemode does not fix this... resetting firefox does not fix this, deleting sandbox and starting with a default profile does not fix this. It always happens after loading a number of tabs at once, say 4-12 tabs of www.whatreallyhappened.com... that recreated it for me. Other times it just starts randomly. Setting Firefox Sandbox to 0 does not fix this. Running firefox outside of sandboxie fixes this.

Ben Hier · Answer

For months I had this same issue with 25% or higher CPU rate. And yes, the same issue came up several times on this forum, even with earlier versions of both Sandboxie and Firefox. As Sophos, I don't have a solution as well. But I got a good workaround for I think most regular cases: 
 - Tweak and build your Firefox: including bookmarks, history, add-ons, etc. always unsandboxed. Cleanup all unwanted cookies/trackers, etc 
 - ALL of Sandboxie must run with NO other software compatibility. 
 Firefox sandbox: 
 - Disable immediate Recovery in firefox Sandbox. 
 - Delete Invocation---->CHECKon Automatically delete contents of sandbox 
 - Leader Program Start AND Stop Firefox and check in Applications that Firefox will be forced. (has been automatically implemented when setting up Leader in most cases) 
 - set File Migration at least at 1700000 kB. (Besides 'the' CPU issue) It prevents CPU fluctuations/flips and it increases Firefox' stability. 
 - Restrictions--->Drop Rights from...CHECK on 
 - Restrictions--->Network Files...BLOCK network files 
 I'm running Sandboxie 5.33.6, but this workaround worked for 5.33.3 as well. Greets!

Ben Hier · Answer

!! I forgot one important thing, which increases Firefox' performance, decreases crashes and robusts leak protection: 
 Program Start--->Forced Folders-->force Mozilla Firefox ( "C:\Program Files" folder in most cases) 
 note: The tweaks I described above do increase performance of other browsers as well. Besides my favorite browser, Firefox, I noted better performance as well with Google Chrome and Brave browsers. The Forced Folders tweak is with these chromium based browsers even more important: They leak if you ONLY force the executable file. On the other side, they are more stable in the case you want to keep their sandboxed files. Greets!