The Firefox web browser is available as a 32-bit and 64-bit application for all supported desktop operating systems including Windows.
The 64-bit Firefox version for Windows is a fledgling however when compared to the Linux and Mac OS X versions, as it has just been available officially since December 2015.
64-bit builds for Windows were available years earlier, and third-party forks like Waterfox or Pale Moon offered dedicated 64-bit versions long before Mozilla considered offering them officially on the main download hubs of the browser.
While Firefox 64-bit builds are available officially on the stable channel, the main download page still pushes 32-bit versions to user PCs.
64-bit versions of Firefox offer better security and better performance for demanding web applications.
Firefox users on Windows are running 32-bit versions of the browser basically, unless they have downloaded the 64-bit version of Firefox for Windows explicitly.
As far as stats are concerned, Mozilla did a market analysis back in 2015:
The stats will have changed since then. Firefox 64-bit for Windows has been released to the stable channel. While downloads are still hard to find, it seems likely that the availability increased the number of 64-bit Firefox on 64-bit Windows.
Most processors are 64-bit that get sold these days, and this will impact the stats as well over time.
Mozilla plans to put the focus on 64-bit versions of Firefox for Windows in the near future. The organization released a proposed schedule that highlights how it wants to accomplish that.
Note: These are proposals, and things may change along the way.
The percentage of 64-bit versions of Firefox on Windows will pick up pace once Mozilla makes the version of the browser a default option in the installer, and when the upgrade of 32-bit versions of Firefox to 64-bit begins. (thanks Sören)
Now You: Do you run a 32-bit or 64-bit web browser?
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Ghacks is a technology news blog that was founded in 2005 by Martin Brinkmann. It has since then become one of the most popular tech news sites on the Internet with five authors and regular contributions from freelance writers.