How To Reduce Memory Usage in Mozilla Firefox


If you’ve noticed a sudden slow performance in Mozilla Firefox, take a look at these under-the-hood tips and tweaks to reduce memory consumption, boost performance and browse faster.

How To Reduce Memory Usage In FireFox


1 – Check For Updates

Ensuring that your internet browser is updated to the latest version is crucial. Updates maintain security, usability and improve the browser’s overall performance and functionality. To install the latest version of Firefox, click here.

You should also keep your installed plugins and extensions updated to maintain usability, security, and performance. Go to Main Menu > Add-ons > Plugins. From here, you’re able to identify outdated plugins and update them.




2 – Disable Unnecessary Extensions

Speaking of extension updates, you should also disable any extensions that you rarely use. Additional extensions use a lot of memory, thus slowing down the performance of Firefox.

To view and disable your extensions – go to Menu > Add-ons. This will display all of the extensions you have installed and will allow you to disable them with ease.




3 – Reduce Session History

By default, Firefox stores up to fifty pages in the browser’s session history. This means that you can travel through fifty pages you’ve previously visited by using the Back and Forward buttons. Although this sounds incredibly useful and convenient, we have to consider how much memory is being used as your page history grows.

In reality, most of us probably revisit a maximum of five pages by using the Back button, so the other forty-five are essentially wasting memory. Here’s how to change it.

  1. Type about:config in the URL bar of Firefox,  which allows you to modify the preferences.
  2. Hit ‘CTRL + F‘ on the keyboard, and enter browser.sessionhistory.max_entries.
  3. Double click on the current value (usually fifty) and change it to a preferred value (I recommend five.)




4 – Keep Tabs To A Minimum

Having numerous tabs open simultaneously can have an enormous impact on the performance of your browser. Consider reducing the number of tabs you have open by using bookmarks or simply close non-essential pages.




5 – Minimise & Free Memory

Mozilla Firefox has an extremely efficient tool integrated into the browser which allows users to minimise memory usage, improving the performance of the browser. To free up some memory, follow these simple steps.

  1. Type about:memory in the URL bar of Firefox.
  2. Under the “Free Memory” section of this page, click on the ‘GC‘ button.
  3. Next, simply click the ‘Minimise Memory Usage‘ button.




6 – Change Preferences via. About:Config

If you type about:config‘ into the URL bar of Mozilla Firefox – you’ve unlocked god mode. Throughout the about:config page lies hundreds of handy tweaks, allowing users to change the entire functionality of Firefox.

If your browser is running slowly, you can use these tweaks to boost the performance and reduce memory usage and consumption. To access these preferences, simply type about:config into the URL bar and press enter. If you see a scary “Here be dragons” page – don’t worry. Simply accept the risk and only change the preferences you see below.

Finally, search for each of the preferences mentioned below and double-click on them to change the default value.


  • browser.tabs.animate – Set to ‘Disable.’ This disables the tab animation feature.
  • config.trim_on_minimize – Set to ‘True.’ This feature will give some RAM back if Firefox is minimised for a while.
  • browser.cache.memory.enable – Set to ‘False.’ This will disable images and pages from being cached – reducing memory consumption.
  • security.dialog_enable_delay – Set to ‘0.’ This disables the delay when installing new extensions.




7 – Enable Safe Mode

If you think that an installed theme or extension is causing an issue with performance, Safe Mode may save you a lot of time. This handy feature will disable all of the themes and extensions that are currently running in Firefox.

  1. First of all, go to the Main Menu and click on the Help Menu button (the button next to Customise.)
  2. Next, select ‘Restart with Add-ons Disabled…

This will restart Firefox and disable all of your installed themes and add-ons.




8 – Regularly Clear Your Browsing History & Cache

Most browsers have been designed to store and cache the content of websites you visit. Although this feature speeds up web browsing, it can eventually affect the performance of the software itself. To clear your browsing history and cache, follow these simple steps.

  1. Firstly, go to Main Menu > History > Clear Recent History (or hit Ctrl + Shift + Delete.)
  2. Secondly, select ‘History‘ and ‘Cache‘ from the list of checkboxes.
  3. Click the ‘Clear Now‘ button.




9 – Restart Firefox

Although this sounds like an obvious one – it’s often forgotten. Over time, Firefox builds up heaps of cache and memory, clogging up your RAM. Simply restarting the browser can be a quick solution to slow performance.




10 – Firefox Refresh

Another useful tool in Firefox includes the ‘Refresh‘ feature. This function will give Firefox an automatic tune-up, almost restoring it to factory defaults.

This process will erase a lot of information, including themes and extensions, download history, security settings, user styles, etc. However, some data will be kept. This includes browsing history, saved passwords, bookmarks, etc.

Before you begin, please make sure you understand exactly what this feature does. You can read more about refreshing Firefox here.




11 – Consider External Applications

If the suggestions mentioned above are not effective  – consider other applications that are running on your system. If several applications are running simultaneously, it can have a huge impact on the performance of your system.




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