Over the last couple of weeks, Mozilla has finally stepped up its 64-bit testing process. There are now five slaves dedicated to building Firefox for Windows x64, which means that from Firefox 8 and onwards, you’ll be able to pick up 64-bit builds that are functionally identical to its 32-bit cousins but operating in native 64-bit CPU and memory space.

Update 25/11/2011: It seems the 64-bit build of Firefox 8 for Windows never came to fruition — and we’re not sure why. You can grab a 64-bit build of the current Nightly, and it works very well, but there’s no word of when Windows x64 will be officially supported. One day, perhaps.

When I first took 64-bit Firefox for a workout last year, it wasn’t the best of experiences: it crashed, JavaScript performance was abysmal, and it was generally sub-par compared to the stable, 32-bit branch. Today, however, Firefox 8 64-bit is stable and it’s fast; it’s really, really fast. Even more importantly, though, there are now stable 64-bit browser plug-ins for Flash and Java. In other words, there’s very little reason to not use Firefox 8 x64; you can download a copy from the Nightly site (it won’t interfere with your stable install), grab Flash 11 beta for Windows x64 and Java 6 for Windows x64, and start surfing. It’s that simple.

Just how fast is the 64-bit version of Firefox 8? About 10% faster than the 32-bit version — but instead of taking our word for it, take a look at the comparative results from the Peacekeeper suite, the most comprehensive browser benchmark. The following results are from the ExtremeTech test rig which houses an Intel i7 930 with 6GB of RAM and an Nvidia GTX 460.



Firefox 8 32-bit (left) vs. Firefox 8 64-bit (right) Click either image to zoom in slightly

The results speak for themselves: Firefox 8 64-bit is about 10% faster than Firefox 8 32-bit. The 64-bit build beats the 32-bit build in every regard except for the Data benchmark, which tests the JavaScript engine’s alacrity with arrays. The Social Networking benchmark is also JavaScript-intensive, but it tests encryption and filtering functions, which the 64-bit build seems to be better at. The most evident and important improvement is in the 64-bit build’s handling of the DOM Operations benchmark; it’s almost 25% faster, which results in almost every dynamic website loading faster and feeling more responsive.

In other benchmarks, the difference between 32- and 64-bit builds is less noticeable. Most IE Test Drive benchmarks resulted in similar scores, with the 64-bit build sometimes creeping ahead by a few percent. With the slightly-dated SunSpider JavaScript benchmark, Firefox 8 32-bit was about 5% faster than its 64-bit brother: 171ms vs 180ms. With the Kraken JavaScript benchmark, however, the 64-bit build destroys the 32-bit version by a good 10%. In almost every regard, then, the 64-bit build seems to be faster than the 32-bit build — and while it might be entirely objective, the 64-bit build really does feel faster too.



Firefox 8 32-bit (left) vs. Firefox 8 64-bit (right) Click the image to zoom in slightly

Memory-wise, the story isn’t quite so happy: the 64-bit build of Firefox definitely uses more memory. With the same set of tabs, Firefox 64-bit had a memory footprint of 320MB, compared to just 230MB for Firefox 32-bit. The plugin-container was also twice the size under Firefox x64: 100MB when playing a YouTube video compared to 50MB for Firefox 32-bit. This could be due to the 64-bit build of Flash Player, however — or it could be that the new memory management features in Firefox 8 have not yet been turned on in the 64-bit build.

It’s important to note that Mozilla doesn’t yet support 64-bit Firefox, but with an army of Windows 64-bit build bots now churning out test and Nightly builds, the wheels have certainly been set in motion. The earliest we’ll see an official 64-bit build of Firefox for Windows is with Firefox 8, which is due in November. Still, if you’re not using your computer for mission-critical work, download a 64-bit Nightly build of Firefox for Windows and give it a spin. You will be pleasantly surprised.

It’s crazy: almost every modern computer now has a 64-bit processor under the hood, but only Firefox on Linux and Safari on Mac are 64-bit applications; 64-bit Chrome and Opera simply don’t exist, and the 64-bit version of Internet Explorer 9 has a broken JavaScript engine. Some 90% of desktop and laptop users are still using Windows machines, and the bulk of their time is spent in a 32-bit version of Internet Explorer, Firefox, or Chrome. With 64-bit Firefox it looks like the vast majority of computer users might finally start using the full potential of their hardware, which is certainly a good thing.