Firefox 4 Supported Platforms Announced, 32-bit only

Martin Brinkmann
Sep 6, 2010
Updated • Feb 24, 2015

Windows users who had hoped for a 64-bit version of the upcoming web browser Firefox 4 will be disappointed as Mozilla decided to postpone the 64-bit version for the operating system.

While some experimental 64-bit builds have made their way on development servers there was doubt all along if Mozilla would be able to deliver both 32-bit and 64-bit Windows versions of Firefox 4.

Mozilla director of Firefox Mike Beltzner said that Mozilla would "work on delivering those in some future release". The 64-bit version of Firefox 4 was planned to be released for Windows only which seemed logical considering that roughly 50% of Windows 7 users selected and installed the 64-bit edition of the operating system.

The chance to be one of the first browsers to offer a 64-bit version is still there considering that only Microsoft and Apple have made available 64-bit versions of their Internet Explorer and Safari web browsers.

To be fair, Opera is also offering downloads of 64-bit FreeBSD and Linux versions of the Opera browser on their website.

Users of a 64-bit operating system can naturally run the 32-bit editions of the web browser in the meantime.

Additional Firefox 4 support related decisions have been posted in the announcement, they include:

  • No support for all Mac OS X operating systems prior to 10.5 Leopard
  • No support for Microsoft operating systems prior to Windows 2000
  • Dropping support for OSX / PPC, Firefox 4 ships as universal builds for i386 only.

Finally, the developers are discussing the option to drop support for i386 architectures that do not support SSE2. No decision has been made on that yet.

To summarize Firefox 4's supported platforms:

Microsoft Windows

  • 32-bit builds only
  • minimum version: Windows 2000
  • CPU architecture: i386, x86-64

Mac OS X

  • 32- and 64-bit builds (universal binary)
  • minimum version: Mac OS X 10.5
  • CPU architecture: i386, x86-64


  • 32-bit builds only
  • minimum version: tbd
  • CPU architecture: i386, x86-64

Firefox users who want to keep an eye on changes to the supported platforms may want to bookmark the official Wiki page.


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  1. Kirk M said on November 10, 2010 at 6:52 pm

    Your supported platforms list is not quite correct as 64 bit versions of Firefox are already supported for the major Linux distros or at least for Ubuntu and Ubuntu based distros. I’m currently running Firefox 3.6.12, 64 bit on Linux Mint 10 RC (derived from Ubuntu 10.10) with 64 bit Flash (Square) and 64 bit Java plugins (among others). Absolutely stable and trouble free. I’m also testing the 64 bit nightly builds using the same above mentioned plugins. Also stable and trouble free so far.

    1. Kirk M said on November 10, 2010 at 6:55 pm

      Small correction to above comment. I meant to say that I was also testing 64 bit nightly builds of Firefox 4 using the same above mentioned plugins. Sorry about that.

  2. BalaC said on September 7, 2010 at 5:38 pm

    Martin, in case of linux minimum version: tbd

    Is that To Be Decided later.

    1. Martin said on September 7, 2010 at 5:38 pm


  3. ReX said on September 6, 2010 at 8:25 pm

    I blame Adobe, nobody is gonna use it without Flash.

    1. ilev said on September 7, 2010 at 6:19 pm

      What flash has to do with FF4 ? iPad / iPhone are doing great without flash.

      1. trlkly said on December 28, 2010 at 10:49 am

        Comparatively speaking, they really aren’t. For example, almost everyone I know is moving to Android phone, considering it an upgrade from their iPhone. And the iPad is not doing nearly as well as it did when it first came out.

        And, anyways, it’s not like people with 64-bit versions of Windows or Linux actually NEED a 64-bit browser. They can run 32-bit versions just fine. So why not develop the more universal version first?

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