Is there a way to determine how much memory each Firefox add-on is leaking?

I found a similar thread on SU here but it is several years old and pretty much all of the add-ons mentioned are no longer in development.

I use Firefox as my primary browser and within a day or two the memory usage is over a gigabyte which is a bit ridiculous.

I don't have a ton of add-ons (in my opinion) but the list of what I use is below:

  • AdBlock Plus
  • Autopager
  • Download Statusbar
  • DownloadHelper
  • Greasemonkey
  • IE Tab 2
  • ImageZoom
  • LastPass
  • Restart Firefox
  • StumbleUpon
  • TreeStyle Tab (can't live without this one and is the only thing keeping me from switching to Chrome)

From what I've read AdBlock Plus leaks a lot of memory but it makes life on the web so much more enjoyable that I'd really prefer to keep it.

I'm running Windows 7 Pro 64-bit.

  • 1
    You may want to see this thread too: stackoverflow.com/questions/171565/…
    – A Dwarf
    Jul 13, 2011 at 12:03
  • I think there's a way to do this with Process Explorer, but I haven't done it myself.
    – Iszi
    Jul 13, 2011 at 13:58
  • But when I close those tabs in Chrome I get the memory back at least, which doesn't seem to happen with Firefox. Jul 15, 2011 at 12:20
  • Process explorer will only help for plugins, not extensions (aside from the few with binary components). Extensions get run as browser chrome, which relies on the same rendering and interpeting functions used to render webpages - process explorer simply won't have the visibility into Firefox's javascript engine to tell you anything useful.
    – Stephanie
    Jul 17, 2011 at 6:16
  • Here is a hall of shame for start-up time impact (via). I don't know of tests measuring memory impact on a typical tabbed browsing session, but I agree they are needed.
    – Tobu
    Jul 17, 2011 at 9:55

1 Answer 1


There's been some work towards making about:memory report more information, but as of yet, it doesn't give anything particularly helpful for diagnosing addon memory usage.

That leaves us the various leak testing tools at https://wiki.mozilla.org/Performance:Leak_Tools

Leaks with an addon are probably in it's chrome javascript, making https://wiki.mozilla.org/Performance:Leak_Tools#leak-monitor your first choice to debug these leaks, probably followed by a debug build.

Also, if you are working at debugging leaks, I'd make sure you are working with an Aurora or Nightly build as a lot of memory leak fixes for Firefox itself have been being committed recently thanks to the MemShrink project.

  • 1
    about:memory with compartments (in nightlies, possibly aurora) is beginning to give an idea of chrome js memory vs tab js memory. Though heap-unclassified takes 40% here.
    – Tobu
    Jul 17, 2011 at 8:34

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