Firefox memory leak? It doesn’t have one. Unfortunately, because of the way it’s configured to run out of the box it *looks* like it has one.

Follow these simple steps to get your Firefox memory usage under control.

These configuration changes are a trade-off between internet browsing speed and memory usage. They are most useful if you are multitasking and need Firefox to be less of a memory hog while using other applications.

#1: about:config

Type “about:config” into your address bar to access the hidden configuration options for Firefox.

#2: browser.cache.memory.capacity

Controls how much memory is used to cache pages.

Right click on the page and choose New then Integer and create an integer called browser.cache.memory.capacity and set it to a low number. This controls how many kilobytes of memory are used for the browser’s cache.

NOTE: number in screenshot is too small. Aim for 80% of whatever the default is.

#3: browser.cache.disk.capacity

Controls how much disk space is used to cache pages in kilobytes.

Set browser.cache.disk.capacity to between 5000 or 15000.

128MB to 512M -> 5000.

512BM to 1GB of RAM -> use 15000

#4: config.trim_on_minimize (optional)

Configure Firefox to swap memory to disk when minimized. This will make Firefox less responsive if you minimize/maximize a lot, but it is good if you need to free memory while multi-tasking to other applications.

Right click on the page and choose New then Boolean and create a boolean called config.trim_on_minimize and set it to true. Now when you minimize the window it will free up memory.

#5: network.prefetch-next

Network link prefetch will download all pages with the rel=”prefetch” tag. This uses up more memory than you would otherwise think.

Set network.prefetch-next to false.

#6: browser.sessionhistory.max_total_viewers

This controls how many pages of history are kept in the back/forward buttons. Lower the value to something acceptable. If you do not use back/forward often then you can set this very low.

Set browser.sessionhistory.max_total_viewers to a low number.

Related Posts

Further Reading

Ryan at CyberNet installs 200 Firefox extensions (via Rooster) and checks memory usage. It jumps from 145 MB to 195 MB after two hours (note that this is a worst case scenario).

Mozillazine article on reducing memory use in Firefox.

List of popular extensions that have memory problems.

Leak Monitor extension for detecting memory leaks.