STR. 1. Go to about:preferences#general 2. Disable "Use recommended performance settings" 3. Set "Content process limit" to "1" 4. Restart Firefox to make sure that proper values will be used 5. Go to about:support, look for "Multiprocess Windows" in "Application Basics" section 6. See that it shows "4/4 (Enabled by user)", instead of "1/1 (Enabled by user)"

There is also one error in Browser Console: > TypeError: data.syscallLog is undefined[Learn More] aboutSupport.js:625:1

(In reply to Virtual_ManPL [:Virtual] - (please needinfo? me - so I will see your comment/reply/question/etc.) from comment #0) > STR. > 1. Go to about:preferences#general > 2. Disable "Use recommended performance settings" > 3. Set "Content process limit" to "1" > 4. Restart Firefox to make sure that proper values will be used > 5. Go to about:support, look for "Multiprocess Windows" in "Application > Basics" section > 6. See that it shows "4/4 (Enabled by user)", instead of "1/1 (Enabled by > user)" The numbers are normally for the number of windows, so if you had 4 windows open, 4/4 sounds right to me? Can you clarify your steps?

I know what's wrong, they're simply ghost windows, that I'm seeing, and it's already tracked in bug #1360280, so I'm duping this bug to that one. Thank you very much for showing interest!