4 Useful Extensions to Improve Firefox Memory Usage

It is a known fact that Firefox is a memory monster. It consumes your memory like there is no tomorrow. Load up a few tabs and it starts to slow down (or even crash). This is also the main reason why many people are ditching Firefox for Google Chrome. If you are bothered by this memory issue, but are not able to switch to other browsers because of the heavy dependency on the extensions, here are another 4 extensions that can solve/reduce the memory issue and make you a happy Firefox user (hopefully) again.

1. BarTab

Tabs is the most valuable features in all browsers, yet it is the one that consume the most memory in Firefox. Try to load 10 – 20 tabs and you see your system coming to a stand still. BarTab works by loading only the tabs that you are actively using. When a tab has been idle for a period of time, it will be automatically unloaded to free up memory space. The concept is, you pay (memory space) only what you are using.


When you restore a session with multiple tabs, you can also configure BarTab not to load all the tabs. The tab will only be loaded when it become active.


2. Memory Fox (Windows only)

Memory Fox is a great extension that can provide dynamic ram memory recover and will attempt to reduce and provide retention as an application’s resource demand. It is a Windows only extension, and the best thing is, you can notice the differences immediately. The screenshot below shows the memory usage before and after memory fox is installed. There is an immediate drop of 50% of the memory used.


After the installation, you need to activate it via the menu Tools -> Memory Fox -> Activate Memory Fox. You should see an icon at the status bar after the activation.


3. Load Tabs Progressively

Conceptually similar to BarTab, but functionally different, Load Tabs Progressively limits the number of tabs that can load concurrently. That means, when you restore a session of 20 tabs, only 3 tabs (or other number that you have configured in the Settings) will be loaded concurrently. Once the 3 tabs finished loading, the next 3 tabs will be loaded.


Unlike BarTab, LTP will load all the tabs, so this is useful for those who need all their tabs loaded when they open Firefox, but doesn’t want it to slow down the system.

Note: It seems that the Load Tabs Progressively extension does not play well with the NoScript extension. Be warned.

4. Reload Tabs Progressively

Not to be confused with Load Tabs Progressively, this extension only works when you use the “Reload all Tabs” function. When you reload all tabs, this extension will limit the number of tabs to load concurrently.


In other words, if you set “3” to the maximum number of reloading tabs and there is 4 tabs, “reload all tabs” command doesn’t reload the 4th tab and reload it after the first tab is completely loaded.

Update: Using a new profile

By creating a new Firefox profile and use that profile for your usual browsing will also reduce the memory usage. Thanks to Wallace for providing the tips.

When you first installed Firefox and used it, it will create a default profile to store all your settings. Wallace has found that by creating a new profile (other than the default profile) and use it as a replacement for the default profile, things start to go easy on the memory.

To get the best out of both worlds, you can even run two instances of Firefox, each with a different profile (not the default profile). Share the loads between the two browsers to reduce the chances of the browser crashing. Two instances of Firefox from two profiles, each with 20 tabs open, causes much less thrashing than one instance with the same 40 tabs open. Idle memory usage will be higher with two instances, so it may only work well on systems with 1GB memory or more.

Note: To use multiple instances of Firefox concurrently, you will need to start the Firefox browser with the command

What other extensions/methods do you use to improve the memory usage in Firefox? For Chrome users, will these extensions pull you back to Firefox again? Hit it in the comments.

Image credit: Rodrigo Hashimoto


  1. It is a shame that Firefox does not do more to improve performance. Many of these tweaks are beyond the abilities of the typical user and a waste of time for the more advanced user. I fell in love with Firefox and tabbed browsing. I now use Chrome on a daily basis for the spartan interface and performance.

    1. Most of these tweaks involve installing a few extensions (and then, only if you want, tweaking a few settings). If that’s beyond your abilities, please stop using the Internet.

      1. I understand your point. Although, you’re being a bit of a smart-a$$. ;-) People shouldn’t have to install extra extensions – that could easily have memory leak issues of their own – in order to plug holes that could, and *should*, have been fixed long ago.

        Don’t get me wrong – I’m a fan of Firefox and have been using it as my primary browser for as long as I can remember. However, after recently installing the new version, FF4, memory usage is out of control – not only for the browser but also for plugin-container. With only 9 or 10 tabs open, the total memory usage easily exceeds 600-700 MB’s within the first 10-15 minutes of opening the browser. That’s not only ridiculous, it’s unacceptable given all the changes they made since v3.5/3.6. Apparently, eye candy was more important to the Mozilla developers than deeper improvements in coding.

        I still prefer FF over other browsers but am disappointed that end users are still forced to patch well-known, long-term holes with duct tape, super glue, masking tape and Spackle (extensions). They serve the purpose of a band-aid and merely cover up the problems instead of fixing them permanently.

        I only hope the developer of BarTab releases an update very, very soon. It’s an invaluable extension but has severe compatibility issues with FF4.

        On a side note, I enjoy the blog. Keep up the good work…

      2. Nice job perpetuating the stereotype off IT guys being pr1cks.  “If you don’t understand it like I do you then you are stupid and should quit.”

        Thanks for contributing to the solution Mr. Helpful.

  2. I switched to Chrome some time back, but I still need to go back to Firefox in many occasion, mainly because of the extensions.

    Firefox 4 has better memory management than the current version of Firefox, so hopefully these extensions won't be necessary then.

  3. When even leaving Firefox running overnight causes excessive memory usage, it’s not good. I just had to close Firefox; it was using 900,000 Mb RAM! I’ve almost made the switch away as well….

    1. You say your instance of firefox was using ~100GB of RAM? Funny, a 32-bit program doing that.

      1. I’m sure he meant KB which is ~.9 GB. Still way too much.

  4. FYI, BarTab caused a problem on Firefox 4 for me. Every so many minutes, the tabs that contained sites that autorefresh (NY Times, Remember The Milk, etc.) would spawn a new, empty tab….they kept popping up. I disabled the addon…things cleared up. After reading this article, I enabled it again…and the problem reappeared.

    1. Will have to contact the developer to fix this issue. When this article is written, Firefox 4 is not yet available. It was a good extension then, but I guess the developer didn’t/haven’t upgrade the extension.

  5. Actually Firefox 4 is far worse than 3.x on memory. It’s similar to WebKit-based browsers like Chrome, while the 3.x series was the slimmest out there.

  6. I don’t know what memory problems you guys have in FF4, i’m on a mac, and it takes 800mb of my RAM ( I have a stat monitoring tool istat). But on Chrome, it goes to 1.1GB, and both with just one tab, but ff4 with 4 extensions and chrome with 1 extension. The best I have so far is Opera with 750 mb

    1. firefox 3.6.18  –  522 tabs open …….memory using 193.971 kb (193mb)

  7. I find that Firefox 4 in 32-bit mode on my mac starts up with 100MB less RAM usage. 356MB in 64-bit mode vs 258MB in 32-bit mode. That’s 28% less memory usage. I expeded it to be closer to 35-40% less just for the fact of the memory addressing used for 64-bit applications but I guess not. Either way I’m gonna continue to use Firefox 4 in 32-bit mode, 1 to save RAM, and 2 to keep from restarting it in 32-bit mode when something like Silverlight needs to run.

  8. Using Firefox 4 now, usually sit around 300 – 400MB, this with a few permanent tabs (webmail and such) and multiple (5 – 10) tabs I keep changing (quite often). Same for the beta of Firefox 5. On my main machine I still sit at Firefox 3.6.17 and rarely reach the 1GB mark, even when having 80+ tabs open. And yes I got multiple addons on both FF4 and 3.6.x, which include firebug, ghostery, adblock plus, tab mix, and some others… While the mem. usage could be lower in my opinion, other browsers aren’t much better either. They all have their pros and cons. I like FF because I’m used to it, and dislike some of the features of other browsers.

    IE because it sucks at supporting the web-standards.
    Chrome because it does things on the background I don’t like, e.g. auto update
    Safari dislike the ui interface very very… very much.
    Opera is my second choice, similar looks as Firefox 4, good support for web-standards and fairly fast.

  9. each new version of FF becomes a worse memory pig than the last. Visiting any mozilla pages will tell you that’s it’s really all the users’ fault. After a noble beginning, they’re just another dimwit corporation now, focusing on the gadgetry while basic functionality goes downhill.

    1. After day 1 of using Memory Fox, it looks like it’s working well. So maybe I won’t have to stop using FF after all. I was going to maybe switch, not to Chrome (because you can’t trust google) but to the more privacy oriented adaptation ->> Iron Browser. Even so, I hate the minimalist interface approach – I don’t want my browser to have to look like a music player, I want to CONTROL things without searching for the controls, if they even exist.

      Btw, Opera is a memory pig now, too – plus you sometimes have to actually kill the task (with Task Manager) when it won’t shut itself down.

      Very helpful article, thank you.

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