Mozilla to release 64-bit Firefox to stable channel in version 41

Martin Brinkmann
Jul 30, 2015
Updated • Jul 30, 2015

Firefox users who prefer a 64-bit version of the web browser instead of a 32-bit version on Windows will be able to install and use a 64-bit stable channel version when Firefox 41 gets released.

Firefox 41, which will be released on September 22, 2015 if things go as planned, will be offered as a 32-bit and 64-bit version for the Windows platform.

All other channels of the browser, that is Beta, Developer and Nightly, are already provided as a 64-bit version, and that is also the case for the Linux and Mac OS X versions of the browser.

So why is the release, originally planned for Firefox 39 and then 40, delayed again? According to Mozilla, it is because of other improvements and changes launching in Firefox 41.

The organization mentioned sandboxing and NPAPI whitelisting in particular which it aims to deploy with Firefox 41.

One difference between 32-bit and 64-bit versions of Firefox for Windows is that the latter will restrict plugin access through the use of a whitelist.

firefox 64-bit

Mozilla plans to put Flash on the whitelist, and maybe also Silverlight according to the official bug report on Bugzilla. Additional plugins are not mentioned which means -- subject to change as always -- that Java for instance won't work in 64-bit versions of Firefox for Windows because of that restriction.

It is unclear why Mozilla made the decision to integrate a whitelist in Firefox 64-bit for Windows, but the most likely explanation is security.

Firefox users may have two issues with this approach. First, not allowing certain plugins from being installed in Firefox will break some sites or applications. If Silverlight won't be supported for instance, it will break media streaming sites that rely on the technology. While many will move over to HTML5 eventually, it will take a while before the majority has completed that process.

Second, leaving Flash, one of the most dangerous plugins enabled in Firefox means that the browser is still open for plugin-based attacks.

Shumway, Mozilla's Flash replacement, is still not ready for primetime and it is unclear if it ever will be.

Some Firefox users will notice disruptions when they start to use the 64-bit version of Firefox for Windows due to this limitation. A workaround is not provided yet other than using the 32-bit version of the browser instead which is less restrictive.

Eventually though, NPAPI plugins will go away just like they did in Google Chrome for the most part.

Now You: What's your take on Mozilla's decision to limit plugin use in 64-bit versions of Firefox for Windows?

Mozilla to launch 64-bit Firefox 41 to stable channel
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Mozilla to launch 64-bit Firefox 41 to stable channel
Mozilla plans to launch the 64-bit version of Firefox for Windows to the stable channel with the release of Firefox 41.

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  1. Eleventeen said on November 14, 2015 at 2:13 pm

    Hard coded restrictions and removing features are pretty asshole things to do imo. Especially considering 99.9% of firefox users are never affected by plugin vulnerabilities. Especially not power users that seek out special version like 64bit. (Average joe is only gonna click your biggest download now button, not caring about how many bits it is, you can link that to a crippled noob whitelist only version if you must, but leave the power user builds available).

    Hopefully they at least take a smart route about this. Yea we get NPAPI is very outdated, etc.

    But if you must make a new one, make it open and functional/available to all browsers. And get the big partners to have proper releases available for it long before you removing npapi.

    Don’t be assholes like google. Support open software and make it happen and functional for everyone before you deprecate useful features many many people and developers use. Don’t break your browser for hundreds/thousands of legitimate sites just because blah blah npapi. For now, there are no alternatives for many useful legit things like say the unity plugin. So until a new api is made and major plugins get a good release out, take it slow.

    Name it something like OPapi (open plugin).

  2. Mom said on September 20, 2015 at 8:49 pm

    What Dave said, duh

  3. Dave said on August 1, 2015 at 3:46 pm

    You know what would be better than turning plug-ins off? Not scanning the entire system for plug-ins and turning them all on by default. How about plug-ins have to be placed in a plug-ins folder, like with every other program ever made. Is that such a big code change?

  4. Ben said on July 31, 2015 at 6:55 pm

    Good to hear. I’m using FFx64 on W7x64 for a long time now and never had any issues with it.
    Well except that it likes memory, right now my FF runs at 9 GB memory usage :>

  5. Jonny said on July 31, 2015 at 10:23 am

    1600 open tabs here I come!! with (16GB ram)

  6. Jim said on July 30, 2015 at 6:07 pm

    Will FF install in user space now or does it still require admin access?

  7. George Melendez said on July 30, 2015 at 2:57 pm

    Can anyone explain what are the benefits of a FF 64 bit version??? From what I’ve heard it’s suppose to be faster but are there any other reasons to switch??? It also seems that some plugins and add-ons will not work with the new 64 bit version. If this is true then why should I be switching in the first place??? I am on the FF Beta version and it’s already fast so why change???

    1. Decent60 said on July 30, 2015 at 6:26 pm

      64-bit allows better utilization of memory and processes. Really that’s the main point. If you open a ton of tabs and videos and have ADHD, it’ll be better for you.
      With that being said, there are many plugins and addons that aren’t fully supported in a 64-bit version. In which case you won’ t benefit from it at all. However, many 32-bit versions of the software do work on it.
      If you want to give it a try out, using ones like Waterfox (which is mainly a recompiled version of Firefox using 64-bit c++ architect; it uses the same profile as Firefox which means you can’t use it and Firefox at the same time) or Cyberfox (similar to Waterfox but more modified, specifically optimized to work with your CPU architect) to still get the Firefox feel but using 64-bit process.

  8. Tom Hawack said on July 30, 2015 at 12:01 pm

    A lingering 64-bit issue I’ve read concerning Firefox is the way it manages memory, not in the good with ability to handle over 4GB, but in the very way it handles RAM, as if it was doubling allocations in certain circumstances.

    What I can say here with Cyberfox 64-bit (Cyberfox is a Firefox fork with 32-bit and 64-bit versions but also removed/modified/enhanced features) : running sites which call much RAM, the amount called with Cyberfox 64-bit is far, far more than that with Firefox or Cyberfox 32-bit. For example, Google Maps with extensive Earth/Street View eats plenty of RAM, I mean a lot! Well, it swallows far more (I’d say twice) when in 64-bit mode. I don’t know why.

    Surprisingly or not, after cleaning RAM cache if I proceed further and call about:memory then clean it with ‘Minimize Memory Usage’ (or use the dedicated Firefox add-on called ‘Free Memory Button’) I notice after such a scenario as above-mentioned with Google Maps… several hundred MB of rendered memory, as if the browser hadn’t handled allocated RAM correctly. This is above my computing illiterate knowledge : I just observe.

  9. Dwight Stegall said on July 30, 2015 at 11:25 am

    Glad to hear that. Waterfox doesn’t play nice with touchscreens.

  10. michal said on July 30, 2015 at 9:52 am


    could someone explain what’s the profit in going to 64bit in case of firefox? Except memory limitation issue naturally. Is there any practical gain, visible to end user? Thanks

    1. Guest said on July 31, 2015 at 8:48 pm

      I don’t think there is much to gain, really, by going 64-bit Firefox. I switched from 32-bit Firefox to 64-bit Cyberfox, and didn’t notice any performance increase at all. I later switched to 32-bit Nightly with e10s enabled, and the performance boost was huge.

      64-bit doesn’t increase performance, e10s (multiprocess) does. You may also note that you can’t exactly hit the 4GB limit (theoretically) if Firefox is split into multiple processes. You should be able to run 10+GB on 32-bit as long as it’s multiprocess.

    2. Solidstate said on July 30, 2015 at 9:41 pm

      Security is a big reason. ASLR in this day and age is almost worthless with a 32-bit restriction. By moving to 64-bit, the address space increases significantly, and Mozilla can finally take advantage of HEASLR in Windows 8 and above.

      1. webfork said on July 31, 2015 at 6:01 pm

        I concur. There are very few web applications that can take advantage of a 64-bit address space (I suspect there’s few that even use multi-threading) so security is likely the driver here.

        I’ll stick with 32-bit until the dust settles.

    3. Nebulus said on July 30, 2015 at 12:12 pm

      If the code is properly written and optimized, you might get some slight speed improvements, but I don’t think that there is a significant advantage. But, yes, memory limitation removal is the main gain of a 64 version.

    4. Caspy7 said on July 30, 2015 at 11:22 am

      This blog entry from Mozilla describes a few benefits. It seems much of the benefit falls into better performance for large or high performance applications (especially those using asm.js).

      1. michal said on July 30, 2015 at 12:03 pm

        Thank you.

  11. eht said on July 30, 2015 at 8:23 am

    I was tried in due time some of variety of 64-bit ff, bad was most of important plugins like Acestream was didn’t have their 64-bit versions, so I don’t migrated to 64-bit ff.

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