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My Firefox v3.5.2 has loads of extensions (48 total, 33 enabled), also considerable database of visited pages and in general rather old profile. Flash is disabled by NoScript, so this is not an issue.

How to profile which add-ons slowdown things the most?

For example, when I start typing in the address bar I sometimes has to wait for each character to render (cpu load is 100% in the case). Also general slowness.

Is there something like Firefox Addons Profiler which shows CPU and memory usage per add-on and per page?

P.S. Already issued find ~/.mozilla/firefox -iname "*.sqlite" -exec sqlite3 {} "VACUUM; REINDEX;" \;, but with little effect.

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The slowdown you're experiencing when you start typing in the address bar is simply a symptom of having too many history entries. If they're not really important to you, just clear them all. – Hello71 Jul 9 '10 at 2:09

i would install a portable version of firefox and:

  • see how speedy it is without any addons
  • add one extension at a time and see what happens

the more "professional" approach would be to trace (vtune, glowcode etc) what firefox really does. but for normal humans i would suggest the mentioned approach.

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Could also just try a new profile. start Firefox with the -ProfileManager switch – Adam Jun 30 '10 at 15:45
No, I'm looking how to avoid bisection. Also I want to see not just add-ons contributions to slowness, but also pages contributions. "professional" approach is better way to go, but I want specialized tool for Firefox which can should what page is being processed with which add-on. – Vi. Jun 30 '10 at 17:44
Also I'm already using 3 versions of firefox (v3.5.2 bloaty for usual activiy, v3.5.2 clean from separate user account for banks and payments and for special development). And I see that clean version is faster. – Vi. Jun 30 '10 at 17:47
@Adam: true, but with even a clean install it is a bit more cleaner :) – akira Jun 30 '10 at 18:32

Firefox for me tends to degrade quickly and notice it quicker than most people because I'm on an older machine. If you have that many extensions, that many preferences, and it's really old, it's probably time to just make a new profile.

Why? Because Firefox is loading too much stuff. Simple as that. And it's not really that hard.

Option B would be to disable addons one by one until speed isn't bad. If you disable one addon, restart and it's still 100% CPU, then disable another, restart and it's gone, you have just found the rogue addon.

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Probably there are several heavy add-ons that slow things down. I want to know if there are seemingly little addons (like "febe" or "flagfox") which consume resources like if there were big (like firebug, autopager, wot, noscript/adblock). I'll use big and important ones anyway, but if some little and no-so-useful will be found out resource-greedy, I'll disable them. – Vi. Jun 30 '10 at 19:24

What works for me for firefox 3.x and even firefox 8 and 9 is to competely remove browsing history and cache. History can go up to 6 months/1 year back, and I guess searching in it takes even seconds sometimes. Options -> privacy -> clear your recent history -> time range to clear set to "Everything", expand details, and select only "Browsing & Download history" and "Cache", (uncheck the rest, you dont want to loose saved logins and forms history). Click "clear now". Restart firefox.

enter image description here

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It is now about cache and history (I clear them from time to time). It what about investigation which extensions cause the slowdown. – Vi. Jan 6 '12 at 12:49
As I understand it your problem is slow firefox, and my answer will very likely fix it as I had the same issue. You are just incorrectly thinking that the slowness is caused by some extension (which might be, but more likely it's history and cache). So I presume that you don't want to do any profiling at all, you just want to have fast firefox... – xhafan Jul 16 '12 at 10:31

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