Everything you need to know about 64-bit versions of Firefox for Windows

The stock Firefox browser, with that I mean the releases that are available for download on the Mozilla website directly, can be run on 32-bit and 64-bit Windows operating systems. While that is the case, it is a 32-bit application that Mozilla offers on its website.

Update: Mozilla offers 64-bit versions of Firefox now for Windows. Find out how to download and install 64-bit Firefox here.

There are 64-bit versions of Firefox, and they are made available by Mozilla for Linux distributions and Mac OS X. If you are looking for a Windows 64-bit version on the other hand, you won't find it advertised on the official project website, and will have a hard time finding references made to it on the site as well.

That does not mean that it does not exist. Mozilla was about to shut down the building of 64-bit Firefox builds for Windows, but user outcry over this made Mozilla revert the decision.firefox-64-bit-windows

Before we look at that, it is necessary to find out about the differences between 32-bit and 64-bit versions of Firefox, or applications in general.

Difference between 32-bit and 64-bit applications

First, it needs to be mentioned that most 32-bit applications run fine on 64-bit operating systems, but that no 64-bit application will run on a 32-bit system.

One of the advantages of 64-bit software is that it may have more memory at its disposal, provided that that enough is installed on the 64-bit operating system. The physical memory limit of 32-bit versions of Windows is 4 Gigabyte, while 64-bit versions of Windows support more than that. How much more depends on the version you are using. Windows 8 Professional 64-bit supports 512 Gigabyte for example, while Windows 7 Professional 64-bit 192 Gigabyte.

Technically, the 4 Gigabyte limit refers to the addressable memory space which the installed RAM, video cards, PCI memory range and other factors attribute to. That's the reason why you won't see 4 Gigabytes of available RAM on 32-bit versions of Windows even though you have installed that much, as part of it is used by other components. (see this for a detailed explanation)

If you are running Firefox on a 32-bit Windows operating system, it can use 3 Gigabytes of memory at the most. If you run it on a 64-bit Windows system, it can use up to 4 Gigabytes of RAM.

While it is unlikely that most users will run into the limits, new technologies such as web gaming and other real-time activities may increase the RAM needs of the browser, and may push browsers towards 64-bit eventually.

A 64-bit version of Firefox that runs on a 64-bit Windows has much larger limits, from about 8 Terabytes to up to 128 Terabytes. (see this page for more information)

It may take some time until we get there in regards to consumer PCs, but it is not that unlikely anymore that PCs have more than 4 Gigabyte of RAM installed.

Conclusion: if Firefox uses a lot of RAM on your system, you may want to consider using a 64-bit version of the browser to avoid the memory limit.

There may be other benefits: 64-bit applications can perform 64-bit register operations, which is faster than performing the same operation on a 32-bit system.

Firefox 32-bit compared to 64-bit

If you compare 32-bit versions of Firefox to their 64-bit builds on Windows, you will find out that they differ in several aspects:

  • 64-bit builds are only available for the Nightly channel. They are not provided as stable, beta or aurora builds.
  • You can only run "some" plug-ins on 64-bit versions of Firefox, and not all of them. While Adobe Flash and Java will work, others may not if they don't support 64-bit software.
  • The crash reporter is not enabled on 64-bit versions of Firefox.
  • Firefox 64-bit on Windows is not officially supported by Mozilla (which means you are on your own).
  • The 64-bit version of Firefox for Windows is considered a Tier-3 platform by Mozilla, which means that it "may or may not work at any time".


download firefox 64-bit windows

You can download the latest Firefox 64-bit build on Mozilla's Nightly download page. This is the only -- official -- location where you can do so.

Locate the Windows 64-bit (Standard) build on the page and click on it to download it to your system.

Note: Nightly versions of Firefox are not suitable for productive environments. While they are fairly stable, you will run into issues every now and then that may break them.

If you run the browser on a system with Firefox installed, you will notice that it will share the profile with that version automatically. You cannot run both versions side by side at the same time, unless you run one of the two versions with the  -no-remote -p test command (test is the name of the second Firefox profile that you want to load).


Third-party forks of Firefox exist that provide access to a 64-bit version. You can download the 64-bit version of Pale Moon for example. The browser is compatible with all 64-bit operating systems from Windows Vista on and supports all the things that Firefox supports as well.

This may also be an option for Firefox users who do not like the new Australis interface that will be enabled in Firefox 29, as Pale Moon won't switch to that.

Closing Words

Eventually, Mozilla will re-evaluate 64-bit editions of the web browser, and at one point in the future make the decision to move it to a higher build tier and offer it as a stable version next to 32-bit versions of the browser. It is not clear if that will happen in 2014, or later though.

Article Name
Everything you need to know about 64-bit versions of Firefox for Windows
The article looks at the current state of 64-bit Firefox, and provides you with information on the benefits and disadvantages of running it.
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Responses to Everything you need to know about 64-bit versions of Firefox for Windows

  1. smaragdus January 1, 2014 at 10:55 am #

    Happy New Year, Martin!
    All the best to you, to your family and to your great blog!

  2. Dan January 1, 2014 at 11:22 am #

    Happy New Year!

    I prefer Waterfox to stock Fx or Palemoon x64. It's snappier, faster, and generally more stable.

  3. Dwight Stegall January 1, 2014 at 11:59 am #

    Palemoon is a crappy browser. Get Cyberfox https://8pecxstudios.com/ It is 100% faster than 32-bit Firefox due to some code tweeking by Toady.

    • A&L January 1, 2014 at 3:12 pm #

      I've been using cyberfox since it came out, updated often, good support

    • Ron January 1, 2014 at 4:47 pm #

      Everyone has their own opinion. My opinion is that Palemoon is a great browser.

    • err January 1, 2014 at 7:17 pm #

      Got something to confirm his revelations? Do you just trolling?

    • Fractal Zone September 17, 2016 at 6:30 pm #

      I second the endorsement of Cyberfox. It is my default Web browser and I've been using it for many months. I doesn't seem to suffer from major memory leaks as much as the full 64-bit versions of Firefox I've been keeping current for a long time. Waterfox looked interesting, but I have not used it enough to have any opinion about it versus comparable releases of Firefox.

  4. Paul(us) January 1, 2014 at 1:55 pm #

    Martin, I wish you and all the people you work with to make Ghacks.net the success it is a ferry happy new year, but most of all a ferry healthy 2014!

  5. Doeraemee January 1, 2014 at 5:26 pm #

    ferry = very

    Happy New Year to all!

  6. XenoSilvano January 1, 2014 at 6:21 pm #

    The title of this article gave me the impression that it would be about Mozilla's intention to release a stable 64-bit version of Firefox sometime within the year. It was only when I was nearing to the end that I realised that the author had mentioned absolutely nothing of the sort throughout most of the entire article, lol, I thought to myself ‘wait a minute, did I miss something or did Martin leave out a very important detail here?’. Only when you get to the very last paragraph is the possibility of 64-bit version of Firefox even speculated about, Ah man! My expectations were far too high!

    If you have ever bought a product expecting to find an item that was not included into the package then you have a good idea of how I felt when reading this article (who knows, maybe that item got into one of the folds of the packaging or is hiding behind some Styrofoam or something), only after giving up do you flip the cover over to affirm that the item your looking for is indeed advertised on the package do you discover the phrase ‘item not included with product’ written in small letters on the bottom right hand corner(!)

    As much as I would like a 64-bit version of Firefox, I’m just not willing to go Nightly, I’ve been down that road before and I didn’t particularly enjoy it.

    On a side note, I downloaded a couple of 64-bit versions of Firefox based alternative browsers and I couldn’t get any of them running on Windows 8.1, have they worked for anyone else?

    On another note in regards to the browser, I’ve noticed that Firefox 26 keeps crashing whenever I use the search bar, the only search bar related add-ons I am using is ‘add to search bar’, Firefox continues to crash despite me having disabled the add-on, is anybody else getting that?

  7. XenoSilvano January 1, 2014 at 6:40 pm #

    I have no idea why Mozilla would shutdown the development of a 64-bit version of Firefox, 64-bit is obviously the way forward, the most significant benefit being the amount of RAM allocated, most computers now a days come with a 64-bit processor and more and more software development teams are creating software specifically for 64-bit architecture.

    A 64-bit version of Firefox is of interest to me because I recently invested in 8gb of RAM for my laptop, even though that laptop has 64-bit processor it was running on a 32-bit version of Windows 8.1 (lol) which I upgraded from a 32-bit version of Windows 8, I wouldn't be able to get access to all of that 8gb of RAM beyond 4gb due to the limitations of 32-bit architecture and seeing as you can't 'upgrade' a 32-bit OS to a 64-bit OS, I therefore had to resort to installing a clean copy of the 64-bit version of Windows 8.1. I needed the extra RAM because I tend to do some RAM intensive work from time to time.

    Prior to upgrading the RAM I was completely clueless as to what 64-bit architecture meant, so I decided to investigate about it. Now, if my understanding is correct, 64-bit processors run 32-bit programs through ‘emulation’ and not natively, despite there being a marginal performance difference between 32-bit and 64-bit architecture, having a program that was specifically created to run natively on 64-bit architecture is obviously the better choice as opposed to through 32-bit emulation.

    If the people who conceptualised the 32-bit architecture never had the foresight to envision a future beyond 4gb of RAM for the PC of the average user (which is still a more than reasonable amount for the average user), then I can't even imagine what the computing demands are going to be like for the average user in the future using 64-bit architecture, will the PC of average user ever exhaust the limits of that architecture to the point for need 128-bit architecture(!?) given the insatiable nature of human endeavour, I think the answer is yes!

    Yay, and now we all set sail for yet another voyage around The Sun on spaceship Earth, here is to the hope that this endeavour turns out to be a more exciting and prosperous one than the last for all of those who made it out of 20(13) alive.

    • Martin Brinkmann January 1, 2014 at 6:45 pm #

      I think the main idea behind the decision was to use the resources elsewhere, and reevaluate the decision at a later point in time.

      • XenoSilvano January 1, 2014 at 11:43 pm #

        That makes better sense to me, there really isn't much of a need for a 64-bit version of Firefox for the time being.

    • XenoSilvano January 1, 2014 at 11:51 pm #

      I would like to correct the part in my comment where I stated that 64-bit architecture is marginal in terms of performance to 32-bit architecture which is not true, 64-bit architecture excels 32-bit architecture in certain aspects.

  8. Barnassey January 1, 2014 at 10:11 pm #

    Uh the games that have been released on PC the past few months are 64bit. Battlefield 4 Call of duty, the new bioshock infinite side story.

    • XenoSilvano January 1, 2014 at 11:10 pm #

      64-bit architecture does nothing to improve overall gameplay compared to 32-bit architecture aside from improving the processing efficiency (not quality) of video and sound, it does nothing for graphics performance.

      • Barnassey January 1, 2014 at 11:28 pm #

        They arent 64bit to improve graphic quality. but from the simple fact the amount of ram they can use. I never said that it improves anything beyond that.

  9. Karl Gephart January 1, 2014 at 11:28 pm #

    To me, I see 64-bit as the future of browsers as memory demands increase on systems. Mozilla should have no doubt as to their need to devote serious resources to a stable version.

  10. XenoSilvano January 2, 2014 at 12:59 am #

    @Barnassey - I know, I posted that comment because you touched on the topic of 64-bit and gaming, I wanted to add some information to the topic simply to be informative. I was going to mention that but I got lazy.

    You didn't actually mention anything about RAM at all : )

  11. blue.bsod January 2, 2014 at 11:44 pm #

    I did not know the 32b of Firefox had a RAM usage cap when running on a 64b o/s, but from what I recall reading somewhere about Firefox 64b, not all of Firefox extensions can run on the 64b version. Is this true Martin, or did I read something wrong? I knew FF64 ran faster and considering my Christmas gift to myself is a Hex-core 4.6Ghz 16G RAM upgrade from a quad 3.1 4G RAM, but maybe I can get better loading and reactions for all the 30+ extensions I use in FF32b. Any thoughts?

    p.s. Windows 7-64b
    p.p.s Have a Happy New Year Martin!!!

    • Martin Brinkmann January 3, 2014 at 7:32 am #

      I think it is about plugins only IIRC. Most plugins are not available as 64-bit versions, which means you cannot run them on a 64-bit version of Firefox.

      • Blue January 3, 2014 at 5:11 pm #

        Hmm, I installed it anyways and all of my 32b extensions but one got installed to the 64b version (Nightly). The single one that didn't work is a bit inconvenient without it but as with all things, I learn to adapt.

  12. Mike Corbeil February 8, 2014 at 4:05 am #

    -no-remote Firefox command line option:

    I first learned of it at http://www.mozillazine.org, it's knowledge base section, and the option initially was or seemed to be preceded by two hyphens, --no-remote, rather than a single hyphen. So I just checked the website again to verify this and the option is shown as preceded by a single hyphen, albeit two still works correctly.

    Anyway, people can learn a little more about the option and related bugs by doing a Web search of mozillazine.org or kb.mozillazine.org (knowledge base) for "-no-remote". Using the main domain rather than the KB one, people will be able to also get any related forum links, f.e. Those will often be excluded when searching only the KB domain url.

    It's useful and not only for testing purposes. I often make use of it for normal Web surfing when wanting to do some using a different Firefox profile. It permits having and making use of different Firefox bookmarks files.

    MozillaZine is a Firefox user community website, rather than provided by Mozilla; and it's a useful website for FFx users to know about. It's been available for a decade or more.

    Actually, it's for all Mozilla software products, instead of only for Ffx.

    When Ffx users think to possibly have add-on or extension problems, then MozillaZine is a website to check. There's an add-ons compatibility information page, f.e. It lists add-ons for which there're known compatibility problems. Descriptions for the problems are provided. This usually includes which add-ons a problematic extension has compatibility problems with or causes problems for.

    -no-remote isn't an add-on. It's a built-in feature that Mozilla developers intended only for themselves but which any Ffx user can make use of.

    I thought that option only permitted one additional instance of Ffx to be run, but the following page certainly seems to indicate that any number of different Ffx instances can be simultaneously opened.


    Tested. I already had a second instance of Ffx open and just tried with a third profile. Definitely works.

    Making use of different profiles means we can have different bookmarks files. Being able to run more than one instance of Ffx at a time or side-by-side means be able to use different bookmarks files without needing to close or end the first instance of Ffx that a user has started. And being able to do this permits using different profiles for different uses. This, in turn, can help users to avoid creating very large bookmarks files.

    It doesn't seem to be a problem any longer for me, not with the more recent and powerful PC obtained in 2011, albeit a second-hand machine from a few years earlier; plus also using XP. But it used to be a problem to have huge bookmarks files and we could then easily find help at MozillaZine, f.e., where we'd learn that we should export the boomarks file to create a backup of it and then start a new file again, or just clean out what we didn't want to retain for presently used file. Doing this many years ago helped to improve Ffx start-up time quite a lot; but, while there may still be a little start-up delay because my main bookmarks file being sizable, say, it's very bearable today.

    This -no-remote feature has existed with Ffx or Mozilla products for a decade or more and it isn't only for 64-bit versions of the products.

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