The release of Firefox 3.6 will see Mozilla take the fight back to Google's upstart Chrome.

Review updated: January 26, 2010. See also: Mozilla Firefox 5 review

The Web browsing world is exciting again. Google's Chrome browser is faster than fast and there's serious thought that Internet Explorer may actually lose its top spot in the browser market-share wars. But for all the excitement, it would be a real mistake to overlook Firefox; with the release of Firefox 3.6, which is now available, Mozilla's flagship browser is looking better than ever.

Mozilla Firefox 3.5 review

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The just-released final version of Firefox 3.6 is a moderate improvement over previous versions - it's faster and introduces a nifty new feature or two. But at heart, it's the same browser that has steadily gained market share against Internet Explorer for years.

Firefox 3.6 has opened up an even wider speed gap against Internet Explorer, better adheres to Web standards and adds a nice trick or two. Those who favour raw speed alone will still prefer Chrome, but Firefox is clearly superior to Chome when it comes to full-featured Web browsing.

We tested the latest version of Firefox on four machines: one running Vista, one running Windows XP, one running Windows 7 and one running Mac OS X Snow Leopard.

We performed head-to-head testing of Firefox 3.6 against version 3.5, Chrome 4, Internet Explorer 8 and Opera 10 on a Dell Inspiron E1505 laptop with 1GB of RAM and an Intel Core Duo T2400 1.83Ghz processor, running Windows XP SP3.

Firefox 3.6 improved performance

To our delight, we found that Firefox uses considerably less memory after prolonged use than its predecessor, Firefox 3.5.6.

Better memory use may not strike you as the most exciting thing about a Web browser, but if you're a serious Web user, with multiple tabs open at once for hours at a time, it's a big deal.

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We have noticed memory issues with Firefox 3.5.6 that slowed a PC's overall performance.

In our testing of 3.6, these memory problems appear to have been fixed, and that alone makes it a "must upgrade" in our book.

We also noticed that the new Firefox is much faster than the last version. Part of this speed boost comes from Firefox's new ability to run scripts asynchronously.

In the past, Firefox waited for the first script on the page to download completely before running the next script, no matter how long it took to download.

Now, Firefox runs whichever script downloads first, no matter where it's placed on the page. It's one of those small changes that make a big practical difference on pages with multiple scripts.

Using the SunSpider JavaScript benchmark, I found that version 3.6 was faster than 3.5 by 12 percent. It was nearly three times as fast as Opera and nearly four times as fast as Internet Explorer.

But it still lagged behind Chrome by approximately 40 percent. I performed the tests three times for each browser and averaged the results, shown here.

Firefox 3.6 Java web browser speed tests

Even though Chrome beat Firefox by a wide margin when it comes to speed, Firefox appears to be better than Chrome when it comes to memory footprint when multiple tabs are open, at least according to my tests.

With five identical tabs open in each browser, Chrome used 194.6MB versus 100.3MB in Firefox. That is partly by design, though, because Chrome uses separate processes for each tab, which leads to a larger memory footprint when multiple tabs are open.

The upside of this for Chrome (and for Internet Explorer 8, which uses the same technique), is that when an individual tab crashes, only that tab is brought down, and the browser itself remains running. With Firefox, when one tab crashes, it generally brings down the browser.

Firefox has always been bedeviled by poor memory management, particularly memory leaks. In this version, memory management remains somewhat problematic.

When I launched Firefox 3.6 on my Vista machine with a single tab open to Google, it used 57MB of RAM. I opened five more tabs to different Web pages, and memory use grew to approximately 145MB.

However, after I closed down those additional five tabs, and stayed on my initial Google page, it was still using 81MB of RAM - nearly a 50 percent increase in RAM use over when it launched. Clearly, the memory handling problem still needs to be resolved.

NEXT: Firefox 3.6 new features.

Firefox 3.6 new features: Personas

There's more to a browser than just fast page rendering, and Firefox 3.6 offers numerous new features that I think make it a compelling browser choice.

Users who like to tweak the look of their browser but don't want to dig into the technicalities of Firefox's XUL (XML User Interface Language) should enjoy playing with Firefox's new Personas feature.

Mozilla Firefox 3.6 personas review

This is a one-click Web-based tool that lets you change the look and feel of your browser. You can either roll your own theme or pick one of the more than 35,000 themes that are already available. Personally, I like the plain-old Firefox theme, but if you like jazzing up your browser's looks, you'll like Personas.

Personas are essentially a way to add skins to your browser. Personas change the colour and background graphic at the top and bottom of the browser.

Personas are slightly different than Firefox themes, which also change Firefox's navigation buttons, in that Personas leave the navigation buttons intact. Also, you don't have to restart your browser to add or change Personas, which you have to do with themes. Personas are certainly a nice extra, but they're far from groundbreaking.

You can find Personas by selecting Tools -> Add-Ons -> Themes and clicking Get Themes. (Yes, you get Personas by clicking Get Themes, which is quite confusing.)

When you install a second Persona, two buttons appear near the top of the browser: Undo and Manage Themes. Click Undo to revert to your previous Persona. Click Manage Themes and you'll be able to see all of your installed Personas, switch among them, and uninstall any you want.

Users of previous versions of Firefox were already able to use Personas, but only with an extension designed for that purpose. Now, with 3.6, the extension isn't required.

However, the Personas Plus extension does make it easier to install, use, and manage Personas. Among other capabilities, it puts a small icon on the lower-left portion of your screen that lets you instantly switch themes and browser and install new ones.

NEXT: More new Firefox 3.6 features.

Firefox 3.6 new features: Plug-ins and more

Firefox plug-ins

A more universally useful feature is that Firefox 3.6 will now automatically check to see if your plug-ins are out of date.

This is particularly important, because even if your browser itself is secure, an out-of-date plug-in can be a security hole through which malware crawls.

Mozilla has also set up a Plugin Check page that will show you all of your plugins, alert you about which are out of date, and let you update any of them by clicking an Update button. This page works with earlier versions of Firefox, not just version 3.6.

Since many 21st-century security problems come from outdated plug-ins, this is an important fix.

Firefox 3.6 plug-ins

For example, Adobe Flash, which most of us use for Web video, has had numerous security problems fixed in the last year. With this improvement, even users who don't follow security news will be able to keep their plug-ins up to date and secure.

This is a win/win situation as far as I'm concerned. I'd like to see all browsers implement this feature.

At the same time, though, Firefox's developers are preventing Firefox browser extensions from loading third-party components installed in its internal components directory.

This is because the programmers were finding that many Firefox crashes were actually caused by misbehaving extensions and plug-ins.

To make matters worse, users couldn't access some of these third-party components with the add-ons manager or even disable them.

The long-term gain from this change will be to make Firefox more stable.

In the short run, though, Firefox's programmers estimate that about 1 in 4 current Firefox extensions will need to be rebuilt to work with Firefox 3.6.

I'm more than willing to put up with that for the sake of having a Web browser that won't fail on me when I'm in the middle of work.

In any event, I've discovered that the Firefox extensions that I consider to be absolutely essentially - the Google Toolbar and Xmark's Bookmark Sync tool - work just fine with Firefox 3.6.

As with every new version of Firefox, not all extensions work with it immediately, and some might break, although if past experience is any guide, almost all extensions are ultimately upgraded to work with it.

Mozilla claims that 80 percent of existing extensions will operate. My favourite extensions worked without a hitch, including Xmarks Bookmark Sync, Google Toolbar, the TinyURL extension and the note-taking extension.

Firefox HTML 5 and web standards

Firefox has previously targeted support for HTML 5, and this newest release goes further down that road, with support for playing video in full screen without use of an add-on.

Of course, very few sites use HTML 5 for this, so this is less-than-groundbreaking news. However, if full-screen video play ever catches on, it will be nice to have.

Firefox also now supports the Web Open Font Format (WOFF), which allows custom fonts to be downloaded on the fly from Web sites and displayed as the creators designed them. Again, though, this technology is not yet in widespread use.

Firefox 3.6 maintains a high level of compatibility with Web standards, as evinced by its results in the Web Standards Project's Acid3 browser test.

It scores 94 out of 100, up slightly from the 93 scored by Firefox 3.5. It trails the latest versions of both Chrome and Opera, which each scored a perfect 100.

Internet Explorer scores a lowly 20, but Microsoft claims that there are security problems in designing a browser that adheres to the acid test.


As the gap between traditional desktop applications and SaaS (Software as a Service) applications continues to narrow, this last feature is likely to see a lot of use.

Mozilla Firefox 3.6: Specs

  • PC: Windows 2000, Windows XP, Windows Server 2003, Windows Vista Minimum Hardware: Pentium 233MHz (Recommended: Pentium 500MHz or greater)
  • 64MB RAM (Recommended: 128MB RAM or greater)
  • 52MB hard drive space Mac: Mac OS X 10.4 and later Minimum Hardware: Macintosh computer with an Intel x86 or PowerPC G3, G4, or G5 processor
  • 128MB RAM (Recommended: 256MB RAM or greater)
  • 200MB hard drive space
  • PC: Windows 2000, Windows XP, Windows Server 2003, Windows Vista Minimum Hardware: Pentium 233MHz (Recommended: Pentium 500MHz or greater)
  • 64MB RAM (Recommended: 128MB RAM or greater)
  • 52MB hard drive space Mac: Mac OS X 10.4 and later Minimum Hardware: Macintosh computer with an Intel x86 or PowerPC G3, G4, or G5 processor
  • 128MB RAM (Recommended: 256MB RAM or greater)
  • 200MB hard drive space


This latest version of Firefox is clearly an evolutionary rather than a revolutionary release. Other than a notable speed improvement, not much else is of note. Personas are of moderate interest; the improved HTML 5 compatibility is of little help right now, and may or may not prove important in the long run. That said, we're very impressed by Firefox 3.6. While we still really like Chrome's speed and recently introduced support for extensions, if you're already a Firefox user upgrading is a no-brainer - the speed boost alone is worth the upgrade. If you're not currently a Firefox user, the moderately interesting new features may not be enough of a draw for you to give it a try. But you may want to give it a spin just to try out browsing the Web at full speed. Internet Explorer? Chrome? Look out. Firefox is back in the game again.

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