I previously have show many tips to reduce the memory usage of Firefox. Even show a application that forces Firefox to use virtual memory and cpu to reduce physical memory usage. Most of them reduced the memory usage to a great extent, still i would love Firefox memory usage to around 90 to 120 MB. Below are few tweaks in the about:config that does some tough things.

1. Reduce memory usage when minimize

Do you know Firefox keeps sucking memory each time you minimize your Firefox. This tip will reduce the memory usage when each time you minimize your Firefox.

1. Start up Firefox
2. Type in about:config in the address bar and hit Enter
3. Right click and choose New > Boolean
4. Type config.trim_on_minimize in the pop-up box and hit Enter
5. Select True and hit Enter.
6. Restart your Firefox

2. Fixed the cache capacity

Firefox caches each page so that when you go back to a website so it doesnt need to load the page elements again to redisplayed. By default, this setting was set to -1 which mean, Firefox use the cache memory depends on your RAM size. Reducing the value will minimize the memory usage.

1. Start up Firefox
2. Type about:config in the address bar and hit Enter
3. In the filter, enter this string browser.cache.memory.capacity
4. If you set to 0, Firefox will not cache any pages. If you want to customize to other value, read here.

Note: browser.cache.memory.enable must be True if you decide to change the integer.

3. Limit pages stored in memory

Each time Firefox visits a web it saves the page you visited in memory to let it quickly redisplay when you click Back and Forward button. A slight tweak to a string will remove this feature and should reduce the memory usage.

1. Start up Firefox
2. Type about:config in the address bar and hit Enter
3. In the filter, enter this string browser.sessionhistory.max_total_viewers
4. By default, it was set to -1 which mean, Firefox will automatically decide maximum pages to be stored in memory. Change the value to 0 will stop Firefox from store any pages in memory. If you want to use other value, read here for more info.

4. Less extension the merrier

Thou extensions are really helpful they are the prime reason Firefox to use more RAM. Few badly coded extensions can cause memory leak. Either uninstall or upgrade your extensions to the latest version may fix the problems.

I hope that the following tweaks reduce the memory usage to some extent,. I think you should start beta testing Firefox 3, it’s turning out to be the best Firefox browser up till now.