hi dchyde, at this early state users aren't updated automatically to a different version (it might happen sometime in the future though, but there aren't concrete plans yet).

at the moment you can get 64bit builds just directly from the download repository at https://archive.mozilla.org/pub/firefox/releases/latest/win64/ please also note that no other plugins than adobe flash player are supported in win64 builds.

Thanks for the quick response, philipp. I have some follow on questions.

I am a long-time but not super-sophisticated user of FF and TB. I understood that the 64 bit version had been out in a beta version for a long time. I take it that the 11/3/15 64 bit version available at the link you provided is stable and not beta, but that the plugins and add ons are further away than usual because there is nothing that can carry over from the 32 bit versions?

Is it possible to run both the 32 bit and the 64 bit versions on the same computer now, waiting for observed functionality of the 64 bit version to reach the point where migration appears reasonable to me?

Assuming I can run both, once I feel that the 64 bit version has the functionality to meet my needs, will I be able to use mozbackup to migrate my various personal stuff from the 32 bit version to the 64 bit version?

32-bit Firefox on Windows will update to 32-bit Firefox.

There is talk of a stub installer that will go about installing appropriate version based on OS being used as 64-bit Windows 7, 8, 10 users would be offered 32-bit or 64-bit Firefox.

Also the Win64 Firefox release is not so visible currently as Mozilla is being low key on it.

extensions will continue to work as you're used to - it's just plugins (like silverlight, java and so on) that will no longer be supported in 64bit. win64 is considered stable - the reason that it isn't advertised more broadly at the moment is because some major content providers are still depending on those plugins to make their content available to firefox users and haven't switched to html5-compatible methods yet... if you aren't say a netflix user, depending on silverlight for playback, there shouldn't be much discouraging you from using 64bit yet. the win64bit version will continue to use your current profile. i wouldn't really recommend switching back and forth between 32bit and 64bit builds with a single profile though. in this case it's probably better to update your existing installation to 64bit and download a portable (32bit) version that you can run independent of that: http://portableapps.com/apps/internet/firefox_portable

The Win64 builds were on Beta channel since the 37.0b2 build for QA testing.

The Extensions are not a issue with 32-bit/64-bit Firefox unless there was something specific otherwise.

Plugins whether on Windows, Mac OSX or Linux you need appropriate ones. The 32-bit Plugins will only run on 32-bit Firefox.

Thank you james and philipp. Some fine tuning of my understanding.

It would appear that every website I visit requires java, as my use of no script frequently prompts a message that I have java turned off and cannot use the website whereas others just lack functionality. This would seem to be a major impediment to using the 64 bit version.

I am getting the sense that I should wait until the upgrade system affirmatively offers me the 64 bit version as this will be the point where the limitations you are highlighting for me will have been resolved and it is ready for mass consumption?

hi, javascript is something very different than java & as javascript is an integral part of the browser itself and no plug-in, it will run fine on win64 as well :-)