How To Speed Up Firefox Tweaking Guide

If your Firefox is slow or misbehaving, here are some tweaks to speed it up. These initial steps are a basic requirement to keep it running smoothly and safely – there is little point trying to improve performance if you are using outdated and insecure components…

1. Update Firefox – if you’re not running the latest version you are more at risk from unfixed vulnerabilities and will not benefit from the latest technical improvements:

Select Firefox (or Help from the menu bar) then ‘About Firefox’ and press the ‘Check For Updates’ button. Apply updates if available then retry – the Check message should confirm ‘Firefox is up to date’.

2.  Remove extensions you do not need – the more extensions you have enabled, the slower and less stable the browser may become:

Select Firefox (or Tools from the menu bar) then Add-ons to open the Add-ons Manager. Click on Extensions and, if you no longer need an extension, Remove it – if in doubt, at least Disable it.

3. Update extensions – the easiest way to always keep extensions up to date is to open the Add-ons Manager and click the Tools ‘cog’ at the top then select (tick) ‘Update Add-ons Automatically’.

To perform a manual update, click the Tools ‘cog’ then select ‘Check for Updates’ and apply any that are found.

4.  Disable plugins you do not need – as with extensions, the more plugins you have enabled, the more problems you may encounter:

Open the Add-ons Manager. Click on Plugins and, if you do not need a plugin, disable it. If you disable a specific plugin and ever do visit a site that needs it, just re-enable it. [The only plugins enabled on my system are Shockwave Flash and Silverlight for streaming videos. Amongst my disabled plugins are Microsoft DRM x 2, Quicktime, VLC, Windows Media Player and Google Update – none of which I have ever needed].

5. Update plugins – plugins from third parties such as Adobe and Oracle are often targeted by malicious websites so it is important to keep them up to date (and new versions often include performance benefits):

Follow my guide to update them – it also warns against the possible error when checking the status of a Java plugin.

Now that you have Firefox, extensions and plugins optimized and up to date, progress to the next section.

Backing Up

The next section tweaks your browser configuration by changing or adding preferences in about:config. You should make a note of the ‘before’ and ‘after’ values of each tweak and (highly recommended) backup the Firefox preferences file that contains all these options first – in case you want to revert back to your original settings:

The configuration file is called prefs.js and is located in the system partition (usually C:\ drive):

In Windows XP   \Documents and Settings\<username>\Application Data\Mozilla\Firefox\Profiles\<profile ID>.default\
In Vista and Windows 7   \Users\<username>\AppData\Roaming\Mozilla\Firefox\Profiles\<profile ID>.default\

You may need to show hidden files to view the folder. Close Firefox first and then copy the prefs.js file to another location on your hard drive for backup.

Tweaking Firefox

Open Firefox and type about:config in the address bar then press Enter. Click the “I’ll be careful I Promise” warning button to reveal a long list of preferences.

To change a preference – if it is an integer (number) or a string (text), double click on the preference name and you will be prompted for the new value. If it is a Boolean (true or false) value, double click the entry to switch from true to false or vice versa.

To add a preference (if the preference name is not already listed in your about:config page) right click on an empty space in the about:config window and choose New followed by String, Integer or Boolean depending whether the value of the preference is text (String), a number (Integer) or true/false (Boolean)

Tip: The quickest way to find the right preference is to type part of the preference name into the Filter bar at the top of the config page – this automatically reduces the list to show only those preferences that include the text you typed.

Change or add the following preferences to the new values shown. If the preference is already set to this value then skip it and move on the next. If the preference does not exist then you need to add it:

browser.display.show_image_placeholders: false

Stops the display of placeholders while images are loading to speed up the page. Default is True

browser.tabs.animate: false

Disables all tab animation features (e.g. when you click the ‘New Tab’ (+) button) to make the tab interface feel quicker. Default is True

network.prefetch-next: true

This setting can automatically prefetch (load) the contents of pages linked to by the page you are viewing e.g. to load the homepage in the background, making it quicker for you to view next if you want to.

To take advantage of increased speed when browsing websites which use prefetch, keep this setting at the Default which is True.

[Some view prefetch as a possible security risk and disable it. My current view is that it isn’t a major concern – if a site is bad, it will just load bad stuff on the current page anyway without needing to prefetch it from elsewhere]

network.http.max-persistent-connections-per-server: 8

Increases the maximum number of persistent connections per server which can help speed up loading of multimedia rich sites. Default is 6

network.http.pipelining: true

Can send multiple requests to a server together in order to speed up loading of webpages. This is not supported by ALL servers – some servers may even behave incorrectly if they receive pipelined requests. Default is False

Optional: if you want Google searches in the address bar to search by name and go straight to the right website (e.g. ‘New York Times’ would go straight to the website) rather than just perform a standard Google search, use the Keyword Search add-on (note that the old keyword.url preference that used to allow this is obsolete so an addon is now required to search by name)

Now close Firefox and re-open it to apply all the tweaks.

Personalizing The Tweaks

The above tweaks improve speed and responsiveness in my own tests but your mileage may vary depending on your exact network configuration, sites visited and other software installed. One of the best things about Firefox is the variety of add-ons available but it does mean that there is an endless variety of possible configurations…

In particular the three ‘network.’ preferences may not be a ‘one size fits all’ solution for you – you may need to experiment to achieve the best settings for your particular installation e.g. by changing them one at a time to different values or back to the default setting. I provided the default settings above in case you wish to revert to them.

Enable Click To Play

Plugins (e.g. Flash Player) can consume significant resources and slow down page loading. Click to Play configures all plugins to only load on click which can dramatically increase the speeds of media rich pages.

This feature is not enabled by default at the time of writing but you can enable it via a simple change in about:config – see Activating Click To Play (half way down the page). You can also Add a Button to the Navigation Toolbar to quickly switch Click To Play on or off at the press of a button.

Don’t Load Tabs Until Selected

If you have set the option to ‘Show my windows and tabs from last time’ (in Options \ General) when the browser starts up, it may have to load multiple tabs – keen users may have dozens of open tabs which have to load in full each time Firefox starts. This can really slow down the time it takes to open the browser – a common complaint. To greatly speed up the loading process:

  • In Options \ Tabs tick the ‘Don’t load tabs until selected’ box and press OK – this menu option will still open all your saved tabs when the browser starts but will only load the current tab which can save a lot of time:
‘Don’t load tabs until selected’ – in Tabs menu

Search For Text More Quickly

This isn’t a performance tweak as such but speeding up the way in which you search for text within web pages can make using Firefox seem quicker.

Firefox includes an Accessibility setting that lets you search for text on a page instantly when you start typing instead of having to open the Find/Quick Find bar first – see ‘quicker searches‘ for a guide.

Compact Databases – Advanced Users

Compacting the databases is a hotly debated topic – Firefox should compact the main ‘places’ database itself but, even if it does, there are many other databases which can become fragmented and overly large – these may also impact performance.

See how to compact Firefox databases – this is recommended for advanced users only who are comfortable with backing up (and restoring if necessary) their Firefox profile.

Still Having Speed Or Reliability Issues?

If you have always let Firefox upgrade itself over many years and you still find that it is slow or unresponsive, it may be time to consider making a fresh start by doing a ‘factory reset’ of it – see the ‘Reset Firefox button‘ section of my review for more details. This is very much a last resort due to the amount of reinstallation and configuration that is required afterwards.

Finally, consider whether your expectations are reasonable – I read of people complaining about performance when they have 100+ add-ons installed or 100+ open tabs or are using very old hardware – they may be simply overloading Firefox beyond its realistic limits and would face the same issues with any other modern browser.

In my own testing over the last 2 years, Firefox has beaten Chrome and IE to become the clear winner for systems with limited memory…

15 thoughts on “How To Speed Up Firefox Tweaking Guide”

  1. @Ebony – all these plugins do different things. Silverlight is only for playing Silverlight (usually Microsoft) streams, not for Flash videos.

    To update Flash, first download and run Adobe’s special uninstaller here – – follow their guide to remove the old 10.3 and then install the latest Flash 11.

    You only need Java plugins if you visit Java websites – mainly games nowadays, only about 1 in 500 sites still use it. Otherwise uninstall it or at least disable it in web browsers per

  2. I use Firefox and If anyone can help me I have one problem. For my plugin, I update Shockwave Flash several times and the update icon stays yellow and never changes to green when I view under “Check to see if plugins are up to date”. It’s version is 10.3 r183 and my windows xp is 32 bit. This link shows the same version of flash player and the version won’t even update it’s still the same.
    Can I remove the plugin and just use Microsoft Silverlight plugin instead? Something to still be able to view youtube videos and other videos that aren’t youtube etc.

    Plus I have Java Deployment Toolkit and Java(TM) Platform SE 7 U17 That is 2 seperate plugins so do I necessary need them or no, if I’m going to install Microsoft Silverlight?

  3. Any tips for improving scrolling performance on the Macbook Pro with retina display? Ever since retina has been added to Firefox its been laggy as hell. I know you can turn off retina, but that’s also pretty headache inducing going back and forth from fuzzy text to rich text. Chrome and Safari’s scrolling perform fast in retina, why not FF?

    • @Rob – I’ve heard of a few issues with laggy FF with retina but not so much re scrolling.

      If you haven’t already, look in Options \ Advanced \ General and try switching between disabling/enabling Use Autoscrolling, Use Smooth Scrolling and also disable Hardware Acceleration.

      If that doesn’t help, may have to wait for Firefox 19+ to (hopefully) address outstanding Mac issues unless other commenters can help.

  4. Performed a reset on FF 17.0.1 the other day, turns out several new FF defaults don’t get implemented via upgrade. Cache management for one. Another good thing I found was the FF 17.0.1 reset now drags passwords over! I re-installed the add-ons, resisted hacking the performance like I used to and to my amazement, its fast by default for once. Tempted to enable pipelining to my magic #12, but so far I haven’t had to. Not sure whats up, but FF appears to be finding a good balance.

    • @Scott – Good point about the defaults via upgrade – another one is the removal of ‘Tabs on Top’ option (you keep it if upgrading but it disappears after reset/reinstall).

      A reset can certainly help compared to constantly upgrading – I’ve been impressed with the last couple of FF versions, they spent a lot of time fixing memory leaks and optimizing, definitely on the right track

  5. Not much chance of us figuring out then ;-) However, assuming the game uses Flash Player – disable all Extensions and Plugins except Shockwave Flash then retest. If works, re-enable 1 by 1 to find the problematic add-on and update or remove it.

    It’s supposed to have been fixed but some people report that disabling Flash protected mode still helps.
    Also see – I know you said it works in other browsers but the advice still holds true for Firefox.
    If nothing works, have you tried ‘Reset Firefox’? The nuclear option would be a full uninstall and reinstall of Firefox from scratch (backing up your preferences/passwords etc first e.g. using MozBackup)

    • ok i tryed every suggestion and even uninstalled and reinstalled nothing helps i have found a few people with the same issue.. guess ill dump firefox all together.

    • I’ve run into issues with flash objects before where hardware acceleration caused a blank screen with larger sizes. Mouseover the flash object, right click on Settings. The first tab, un-check “Enable hardware acceleration”. This can be done using youtube videos also. Worth a try

  6. i have this issue with firefox. i play a kixeye game through facebook and the game wont load. it works on several other browsers on the same PC.. kixeye nor mozilla can figure out the issue.. HELP..

  7. Firefox 7 leaves out adjustments for AdBlock Plus and Roboform lite to work, which are two addons that to me are indispensable.

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