4 Firefox rebuilds feed the need for speed

Alternative builds bring speed optimizations and custom features to the Firefox core

Firefox is one of open source's biggest success stories. Not only is it a hit with mainstream users, it's also popular with developers, who've created a number of spinoffs, derivatives, and alternative builds from its code base.

Alternative builds of Firefox exist mainly to take advantage of processor instructions that aren't used in the official Mozilla versions. Mozilla codes Firefox so that it will run on the broadest possible number of machines. But that breadth of compatibility comes with a performance penalty. The instruction sets used by alternative builds -- and unused in Mozilla's official edition -- provide a speed boost.

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Under-the-hood changes in private builds might also include custom features (such as Atelier's portable mode), but just as often they involve disabling standard Firefox features (such as the removal of accessibility extensions and parental controls in Pale Moon) -- again, for the sake of better performance and stability.

Another common reason for alternative builds is to create native 64-bit editions of Firefox, which can address larger memory spaces and in theory perform better than their 32-bit counterparts. It's safe to assume any PC shipped today is running a 64-bit version of Windows, but many apps remain available only in 32-bit editions for compatibility. Firefox is one such app, in large part because of the significant number of 32-bit Windows systems still in use.

I've long been curious about the state of third-party Firefox builds. Here I've surveyed the most prevalent third-party builds to see whether or not they're worth the trouble of swapping in to replace stock editions of Firefox. My criteria for picking these particular builds? First, they're actively maintained. Second, they're optimized for 64-bit systems or, at the very least, just plain optimized for faster performance. And third, they're available in a Windows edition, important because Windows constitutes the biggest installation base for Firefox.

In every case but one, I tested builds that used the 10.0 branch of Firefox. The lone exception, Atelier, is based on the 9.2 version of Firefox. I also ran the browsers against a set of common browser benchmarks:

  • Peacekeeper, a general JavaScript and HTML5 test suite
  • SunSpider, WebKit's JavaScript test suite, which tests core language behavior only (not the DOM or browser APIs)
  • BrowserMark, a JavaScript and HTML rendering benchmark nominally for mobile browsers but also useful for desktop versions

I also tried out the SPDY download-speed test, to compare the browsers that had it enabled (all builds based on Firefox 10 and later) with those that didn't.

The test system was a quad-core Intel Q6600, 2.4GHz, with 4GB of RAM running Windows 7 Ultimate.

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