Light is a slimmed down Firefox third-party build optimized for performance

Martin Brinkmann
Jan 4, 2014
Updated • Jan 14, 2014

I have updated the custom Firefox build list today and stumbled upon a new third-party build that I had not heard about before.

Light is a third-party build of Firefox much like Waterfox or Palemoon are. The core difference between Light and many other builds is that Light is a slimmed down version of Firefox.

What is meant by that? Well, instead of just including everything, or nearly everything, in the third-party build, the author decided to remove components from Firefox.

The following components are not included in Light according to a post made on Mozillazine.

crashreporter skia webm opus ogg wave webrtc jsd gamepad intl-api accessibility webapp sync healthreport safebrowsing pdfjs identity spellcheck tabview social devtools printing webspeech webgl directshow

As you can see, it is a mix of components that some users may rely on, while others may not miss them at all. Components include front-end tools such as Developer Tools, the spell checker, or Firefox sync, but also backend components such as WebGL, WebRTC, support for webm, opus or off, or printing support.

It should be clear that Light is not for everyone because of that. If you rely on a component, say printing or Web Developer tools, then you cannot really use the third-party version of Firefox as it does not offer it.

While you could install Firefox next to it and run it independent from each other as profiles are not shared, it is not the best of options.

You are probably wondering about the benefits that come along with such a stripped down version of Firefox. First, you get a 32-bit or 64-bit build that you can download from the developer's website, or more precisely a connected Google Drive account.

All builds support a portable mode. For that, you need to rename the custom_t.ini file to custom.ini.

Light should feel a bit snappier for most users. The loading of pages feels a bit faster but not overly so, as Firefox is already loading most sites blazing fast. Still, Light feels a bit faster still.

There are not any memory improvements, but if you run a benchmark such as Peacekeeper, you may be in for a pleasant surprise.

In a non-scientific test on my system using Light, Firefox Stable and Firefox Nightly, Light scored the most points with more than 3200, followed by Firefox Nightly with more than 2800 points, and Firefox Stable with more than 2500 points.

A benchmark is not really something that you can translate 1:1 to real-world applications, but it shows that some optimizations went into Light.


The missing components may keep some users from giving Light a try. While you can work around some, for instance by installing Firebug for web development or using a third-party synchronization tool instead of Firefox Sync, you cannot add others to the browser.

Probably the best way to start is to simply download the latest version of Light to your system to take it for a test ride.

The idea is definitely an interesting one, slimming down Firefox to improve performance, and while you may agree or disagree in regards to the removed components, there is no denying that this is probably the snappiest version of Firefox that you have tried until now.


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  1. topkek said on March 4, 2015 at 1:40 pm

    how do i add this to ccleaner?

  2. Rajesh said on January 7, 2014 at 11:22 pm

    Under the drop down menu via help and about light, there’s no way to update from there.

    1. Martin Brinkmann said on January 7, 2014 at 11:23 pm

      As I said, it is likely that you have to download new releases and install them manually.

  3. Rajesh said on January 7, 2014 at 11:09 pm

    Just a quick question, how is this (Light) updated?

    1. Martin Brinkmann said on January 7, 2014 at 11:17 pm

      I think you need to do so manually.

  4. Dwight Stegall said on January 6, 2014 at 11:58 am

    Light Firefox is now using the Australis GUI.

    1. Martin Brinkmann said on January 6, 2014 at 12:46 pm

      It is available for both interfaces.

  5. Srihari Thalla said on January 5, 2014 at 4:35 pm


    Recently, my Firefox is consuming large amounts of memory. When it is around v22.0, it is good occupying around 400-600 MB which is good.

    But right now, it is averaging around 800-1200 MB, and if I continue browsing, I experience a lot of delays in Interface – scrolling, loading components, Dev Tools Console – virtually everything is delayed.

    Not sure what’s going on. I have 16 GB RAM on Win8.1 and right now, the memory is at 965.3 MB. I have been using this browsing session for almost 10 hours, continuously.

    I never experienced this kind of behavior, it started around a month or two.

    And, Light is not for me as I use Dev Console and Sync everyday!!

    1. Martin Brinkmann said on January 5, 2014 at 6:14 pm

      Maybe it is caused by an extension? Anything out of the ordinary, or installed anew that coincides with the RAM increase?

      1. Ken Saunders said on January 6, 2014 at 6:35 pm

        For what’s it worth, you can always contact Firefox support. Some of the volunteers have been around since before Firefox was Firefox.

      2. Ken Saunders said on January 6, 2014 at 6:30 pm

        Certain webpages can do that. I know that Facebook does for sure and others like do as well. RAM usage skyrockets when Facebook is open.

        Add-ons can certainly do it and not simply when Firefox is running, but when you start to use one. For example I use the Web Slide Show add-on and once I use it to view images, RAM usage increases, sometimes dramatically and it doesn’t always release the RAM afterwards. It’s still a good add-on though and worth it.

        For what’s it worth, you can always contact Firefox support. Some of the volunteers have been around since before Firefox was Firefox.

      3. Srihari Thalla said on January 6, 2014 at 6:05 pm

        Thanks Ken, for the links. I will check the addons with the safe mode.

        And today, the browser worked fine for about 8 hours consuming around 400-600 MB and all of a sudden in about 10 minutes, it’s increased to ~1300 MB, and I am forced to restart. Uh oh!!

        May be I should be a hard cleanup of Windows too??!!

      4. Ken Saunders said on January 6, 2014 at 5:29 pm

        Me either, and I only have 4Gigs

      5. Ken Saunders said on January 6, 2014 at 5:02 pm

        This could be helpful.
        Adds an about:addons-memory page that details add-on memory usage

        You could also run in safe mode and enable add-ons one by one instead of creating a new profile but a new/clean profile will run better.

        If you don’t have a lot of add-ons, you could reset Firefox.
        Alt + H + T Reset Firefox..

        I recently cleared everything in Firefox except for passwords (Ctrl+Shit+Delete > Everything) and also used CCEnhancer > CCleaner and Firefox is running even better.

        Oh, one more.

        You could always ask the support team for help too.
        Some the volunteers have been around since before Firefox was Firefox.

      6. Martin Brinkmann said on January 6, 2014 at 5:12 pm

        I do not really experience memory issues in Firefox :)

        Thanks for the links.

      7. Srihari Thalla said on January 6, 2014 at 12:53 pm

        Nothing new in this month. I think I shall try a new profile and with addons one by one. That might give some insights.

  6. imu said on January 5, 2014 at 3:35 pm

    qupzilla get it at and give it a try, for Windows there is portable version available :)

    1. 桜 said on January 7, 2014 at 6:11 pm

      Is ‘Qupzilla’ really a Firefox fork? It looks like a new browser.

      I read that the developer says in December 2013 that ” … haven’t had really much time lately to work on QupZilla.” That is sadly often the case for browsers like this. They tend to fade away. It is probably going to stay as a browser to use as a “hobby” rather than a main browser.

      However, thanks for the very interesting link.

    2. poison said on January 6, 2014 at 6:05 pm

      Nice one! Testing here on Ubuntu 12.10 64bits and its working like a charm!

    3. InterestedBystander said on January 6, 2014 at 12:34 am

      Nice, imu. Just installed under Ubuntu. Monitor reports 114 mb memory usage with one tab open, 235 with 5 tabs open. Pretty snappy preformance. Thanks for the link!

  7. 桜 said on January 5, 2014 at 3:00 pm

    There is no Linux version of this Firefox fork. I think it is Windows only. Correct me, if I am wrong.
    The problem is often that the most Firefox forks lag behind the main FF.
    It is always a ‘personal preference’ choice for the individual. However, the user needs to know the pros and cons of each fork.
    There are now so many Firefox forks that it is difficult to keep track of them all. There needs to be a website or Wikipedia page which just deals with Firefox forks in detail. If anybody has the time to do that work, I will certainly like to read it.

  8. Maou said on January 5, 2014 at 2:19 pm

    I think I´ll stick to Palemoon for now as it suits all my needs. I would love a third party Firefox for Android, I´m hating the new versions because they´re taking away too many options.

  9. jasray said on January 5, 2014 at 2:27 am

    Never really bothered with benchmark tests because of the many variables involved; here are my results for three browsers–all 32bit running on Windows 7 64bit:

    1. Firefox (current install with 22 extensions)
    Peacekeeper = 1741 – HTML5 Capabilities 7/7
    Memory Usage = 245,316

    2. Light (installed from developer’s site with no extensions added)
    Peacekeeper = 1928 – HTML5 Capabilities 4/7
    Memory Usage = 273,960

    3. Superbird (only for fun and rather curious)
    Peacekeeper = 3039 – HTML5 Capabilities 6/7
    Memory Usage = 278,348

    Verdict – Scientifically, the results achieved wherein I would be in for a “pleasant surprise” didn’t occur. My hypothesis is Light would actually perform worse than my current Firefox setup if I were to install all of the extensions.

    The micro-experiment validates earlier hunches I’ve had about Benchmark tests and the Internet–same hardware, same ISP, same bandwidth, same DNS, same Everything needs to be in order before even an approximate generalization can be made about the performance of another new “slimmed down” version of a browser.

  10. InterestedBystander said on January 5, 2014 at 1:39 am

    A bit of Alt-Firefox trivia: if you have an old iBook (OS Tiger, 10.4) then there’s a Firefox fork called TenFourFox. It runs competently on my 2005-vintage G4. Wouldn’t want to use it for everyday, but it adds enough functionality to keep an old Powerbook alive. See for the project page.

  11. pd said on January 4, 2014 at 11:52 pm

    until someone provides a web page with checkbox options for each build flag and a login so it can remember the settings, then a build its generated for exactly what a user wants, these alternative builds are going to always be very limited.

    afaik Mozilla has their ‘try’ server which facilitates this sort of on-the-fly remote access style building of Firefox with whichever patch applied that a developer wants to test. I’m guessing it might be very resource intensive to provide a similar facility to the much broader General public audience as I’ve suggested. however it could lead to a market share increase if geeks are able to use it. what would be cooler than your own custom Firefox build?

    on the other hand it could be a nightmare for web devs who would then be presented with a much wider level of browser compatibility holes. in short, for those build options that effect content, wider use of custom builds would be similar to the advent of many loose planks of wood in the web platform.

    1. fokka said on July 20, 2015 at 8:13 pm

      sounds like an interesting idea that is ridiculously impractical.

  12. Dwight Stegall said on January 4, 2014 at 11:44 pm

    You will find that Cyberfox 64-bit is 100% faster than Firefox in benchmark tests. The Disconnect addon claims to make page loading up to 27% faster. The only problem is Cyberfox will never have the Australis GUI.

    1. Orhin said on January 6, 2014 at 2:27 pm

      No Australis, thats great :)

      Thats the reason why i will use it or Palemoon – Depending which one of the 2 will really be able to avoid Australis. I do not want Mozilla-Chrome.

      Because i still want an addon Bar, not merged Navigation bar icons and i want to make a Nav Bar Clone in the addon Bar and Tab bar.

      Australis takes all that possibilities away from Firefox. And that is more then unaccaptable!

    2. ReX said on January 5, 2014 at 2:03 am

      That sounds like a great “problem” to have.

  13. Caspy7 said on January 4, 2014 at 11:42 pm

    Several of the things in the list don’t make sense to me – removing support for media types and APIs in particular.
    As I understand it, many of these things aren’t loaded, and wouldn’t affect performance, unless directly invoked. If you aren’t playing a webm video or have a Social service installed (it is an API after all, it just *allows* functionality like addon or plugin APIs) then their presence should have zero effect on performance.
    I’m not saying it’s true for everything in the list, but some of it seems like trying to uninstall Java for better performance when you never visit pages with Java on them in the first place. When it’s not in use it remains unloaded.

  14. ReX said on January 4, 2014 at 11:26 pm

    Both Google Code and SourceForge pages having nothing but a short description, containing a link to a shortened link Google Drive page, is kinda raising some red flags for me.

    And I think not having the source code anywhere is a violation of Google Code, SourceForge and MPL’s terms.

    1. Ken Saunders said on January 5, 2014 at 3:09 pm

      Ya, I don’t understand why the developer doesn’t just use SourceForge.
      It’s all an interesting idea, and it is worth an article, and somethings that are removed are understandable, but removing spellcheck to me is just silly.

      Also, you can do whatever you want with the Firefox source code, but you can’t use Mozilla’s trademarks like the developer does with the word Firefox and the logo used on SourceForge.
      Seems to be all over the place too.
      “lightfirefox” “Light”

  15. Sleeping said on January 4, 2014 at 11:10 pm

    Any way to compile Firefox on Windows by myself removing what I don’t need, but keeping what I need (or may need)? :)

    PS: I thought the installer was smaller (just about 19MB VS 22MB)…

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