been a user of ff since 0.9 version when ie6 pissed me off. while using ff i noticed it's consatntly using 1-2% of my cpu even when the active tab is something static. it jumps when doing stuff but the baseline on my core 2 duo 6700 (2,66ghz) cpu is 1-2%. http://i50.tinypic.com/1c8xg.jpg same happens on my quad core nehalem. even with no tabs open i still get that constant noise activity. this is not a big deal on a desktop but on my laptop this for sure drains the battery as it keeps the cpu active. later edit: so... opened a new window with no open tab and closed the first window... cpu at 1,5% mostly and quite stable at this value. opened google home page, closed ff, open again so that there would not be any closed tabs in memory. basically ff started and opened one tab with google search page opened and doing nothing. the cpu was at 2% most fo the time with some seldom spikes to 5-10%. this shows me that the (little) constant cpu usage is not realted to tabs opened, closed. it may be related to addons. however i remeber i opened ff with all addons disabled, no active tabs and still the cpu usage. i'm not sure if this is the internal cleanup activity or activity realted to tabs being active, getting updates, playing music, getting emails... javascript activity. there are cases when somone decide to make some funky snow-falling effect on one page, eating a lot of cpu. that would continue to peg the cpu even when the tab is tot the active one. this would be worse when i would minimize ff to do something else and i would still pay the price. i would expect that the inactive tabs would freeze completely or be allowed to get resources from time to time. the from time to time would be the model windows 8 uses for metro apps. the apps are open but when minimized they get suspended and from time to time the tiles would update. my thoughts - when minimized ff should update from time to time like the win 8 tiles do and use the cpu as little as possbile - the active tab should get the fully required cpu esources but the hidden tabs should either get cycles from time to time or completly freeze is it normal that firefox would use a little of the cpu when nothing is active? later edit: so... opened a new window with no open tab and closed the first window... cpu at 1,5% mostly and quite stable at this value. opened google home page, closed ff, open again so that there would not be any closed tabs in memory. basically ff started and opened one tab with google search page opened and doing nothing. the cpu was at 2% most fo the time with some seldom spikes to 5-10%. this shows me that the (little) constant cpu usage is not realted to tabs opened, closed. it may be related to addons. however i remeber i opened ff with all addons disabled, no active tabs and still the cpu usage.