Identify resource-hogging Firefox add-ons with about:addons-memory
If Firefox seems to be using a lot of memory on your system then a resource-hogging add-on could be responsible, but finding out for sure can be a challenge. Entering about:memory in the address bar will provide lots of figures on RAM allocations, for instance, but they’re extremely technical, more about "heaps" and "compartments" than providing information which most people can actually use.
About:addons-memory is a simple Firefox extension which takes a different approach. There’s no jargon, no unnecessary technical details, just install it (no restart required) and enter about:addons-memory in a new tab for an instant report on your extensions and their memory usage.
The list is conveniently sorted by RAM requirements, so if you do have a problem extension then it’ll probably appear at or very close to the top.
If you’re curious, though, just scroll down the list for details on every extension you’ve installed.
And at the bottom of the report is a "Minimize memory usage" button which may help you free up some RAM, as well as a few notes on what the various figures actually mean.
This all worked very well for us, but if you try the add-on yourself then you’ll need to be careful how you interpret the figures.
Coming top of the list doesn’t necessarily mean an extension is poorly coded or inefficient, for instance -- it all depends what it’s doing.
And about:addons-memory may not be able to determine the full amount of RAM used by all your extensions, so you need to treat its memory allocations as a minimum: some add-ons could be using more. If you’re thinking this limits its usefulness, then you’re right, but about:addons-memory is still a handy way to start exploring Firefox’s memory usage, and well worth installing.