Does Firefox add-ons decreases firefox performance?

If I install and use many addons or if an XPI file is big in size of and add-ons then than that add-on will decrease more performance than small size add-ons.

How do I keep Firefox 3.6 performance good even after using so many add-ons?

Which popular Firefox 3.6's add-ons should I avoid to keep performance good?

  • 1
    I don't think the question is deserving of downvotes - language is a bit unclear, but I think it's a pretty good and legitimate question. – Phoshi Mar 2 '10 at 11:52

That's a question similar to "Will installing software slow down my PC?". The answer, of course, is YesNoMaybe. It completely depends on what the addon is, what it's doing, and how efficiently it's doing it.

NoScript and Adblock Plus, for example, are likely to increase Firefox's execution speed, but decrease its startup speed, whereas many other addons can reduce execution performance, but have no real impact on startup, and many more have negligible impact on both. It's a gamble.


Yes, it does. Some extensions are known for excessive CPU usage.

  • Mouseless Browsing
  • Google Web Accelerator
  • ForecastFox
  • Firebug
  • Adblock

are few to mention ... Please note it may or may not affect your Firefox performance (but it is commonly know for).

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    Firebug is pretty good at doing nothing if it is told to turn itself off, but if you have it active especially with all the options on, it can slow things down quite a bit. From the question though I don't think the user in question is likely to want Firebug installed anyway. – David Spillett Mar 2 '10 at 10:31
  • @David Spillett - I keep firebug always installed. – metal gear solid Mar 2 '10 at 10:39
  • Fairy nuf. Keeping all of its areas off until explicitly needed will reduce its resource use to next to nothing. – David Spillett Mar 2 '10 at 13:35


Besides being proprietary, my Lazarus database is so big that it halts each Firefox start and results in a "Kill Script" dialog to kill it and continue starting Firefox.

I keep this extension because I don't know of a free one that performs the same miracles.

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