Mozilla Firefox 4 is a faster, sleeker, and easier to use web browser. Does it stack up to Google Chrome and Microsoft Internet Explorer 9? Read on. Updated 23 March 2011. 

See also: Mozilla Firefox 5 review

A lot has changed in the browser universe since Firefox 3.0 launched in June 2008. Google Chrome burst on to the scene, and has undergone frequent updates since then. Microsoft released IE 8 and IE 9. Safari advanced from version 3 then to version 5 now.

While Mozilla made some improvements in Firefox 3.5 and 3.6 that improved performance and bolstered the feature set, Firefox started to feel like it was falling behind the curve. Firefox 4 makes Firefox competitive again, with its updated interface and improved performance.

Mozilla Firefox 4: Firefox Gets a Makeover

The first thing you'll notice is that Firefox 4 has a new look. Like many other modern browsers, Firefox 4 is designed to be as streamlined and as simple as possible. The Mozilla designers did a good job at simplifying the browser while maintaining the flexibility that Firefox is known for.

By default, Firefox 4 shows the address bar, a search field, the typical back/forward/reload/home buttons, the tab bar, and an orange "Firefox" button in the upper-left corner. There is no menu bar by default: Clicking the orange Firefox button brings up a single, well laid-out menu that contains most--if not all--of the menu items you're accustomed to using in older Firefox versions. I was a little thrown off by this button, though; most new browsers have their tools menus on the far-right edge of the toolbar, whereas the Firefox button is on the upper-left, but I was able to adjust fairly quickly.

If you're a Firefox power user - or just prefer the old way - you can bring back the classic menu bar by clicking the Firefox button, mousing over "Options," then selecting "Menu Bar" from the drop-down.

Mozilla Firefox 4: Pinning Web Apps

Another Chrome-inspired feature in Firefox 4 is the ability to "pin" Web apps to the tab bar. Open up any Web app (or any Web page, really) in a new tab, right click the tab, then select "Pin as App Tab." This will add a tab showing only that page's icon to the far left edge of the tab bar.

When you close then re-open Firefox, the pinned tabs will remain there. Whenever something in the Web app you pin updates--say, you get a new message in your Gmail inbox--the pinned tab will turn blue to notify you (again, very similar to Google Chrome).

These additions are great if you use lots of Web apps, but they're features that Chrome already has, so it does feel a bit like Firefox is playing catch-up here.

Mozilla Firefox 4: Stop Following Me!

Like IE9, Firefox now includes a feature to prevent sites from being able to track what you do online. This is a welcome addition, but it isn't without its problems. For one, it's an all-or-nothing feature--it's either on or off; there's no way to let some sites through and block others. And it isn't really universal yet: When you enable tracking protection in Firefox, it'll use what are called HTTP headers to tell the site that you don't want to be tracked. A simplified way of putting it is that when you visit a Website, Firefox will send a message to the site that you don't want to be tracked.
The problem is that Websites don't have to honor this request, thus rendering the tracking protection feature useless. Mozilla is working to make this feature an industry standard, so hopefully things will improve in time.

Firefox 4 also sports a number of new features designed to improve page loading and rendering performance. Firefox 4 can take better advantage of your graphics card than Firefox 3.x could; using it to play videos, for example. Firefox 4 also includes an updated JavaScript engine that should improve performance of Web apps and certain elements of Web pages.

We haven't done any in-depth speed testing of Firefox 4, but we did test its JavaScript performance using the SunSpider 0.91 benchmark. Firefox 3.6 completed the test in 1103 milliseconds (ms) on average, which was the slowest among the major browsers (Safari, IE9, Chrome, Firefox, Opera). Firefox 4 completes the test in 363 ms on average, making it competitive with other current browsers (In my testing, all browsers averaged between 329 and 439 ms.)

Granted, your mileage may vary based on your hardware, operating system, and other factors, but there's no denying the fact that Firefox 4 is much faster at handling JavaScript than Firefox 3.6.

Mozilla Firefox 4: Stay in Sync

New in Firefox 4 is Firefox Sync, which lets you sync your bookmarks, browsing history, passwords, and other data with your other computers running Firefox. (This was previously available via an extension called Mozilla Weave.)

To use Firefox Sync, go to the Options Pane (open the Firefox menu and click Options,) then select Sync from the toolbar. From there, you can create a new Firefox Sync account. Setting up an account is fairly easy - it'll ask you to enter your e-mail address and create a password - but things get a little more complicated after that.

Firefox will give you an alphanumeric "Sync Key" that you'll need to write down, save to your disk, or print to keep safe. You'll need this key to be able to access your Firefox Sync account on another PC or smartphone, and if you lose it, you're out of luck--it can't be recovered.

Setting up a second device (PC, smartphone, etc...) to work with Firefox Sync also requires you to jump through some security hoops as well. For example, if you've already set up a Sync account and you want to set up Firefox Sync on your laptop so it stays in sync with what you have on your desktop, you'll need to go back to your desktop and enter in an authentication code.

If you don't have access to your desktop PC at the moment--say it's at home and you're traveling with your laptop--you'll need to enter the aforementioned Sync Key. If you left your Sync Key at home, you can't access your account. This sort of two-factor authentication is a bit of a double-edged sword; it's more secure than a password alone, but it can be a hassle.

Once you get Sync all set up though, it's easy to use. Everything is handled automatically and in the background, so you won't have to manually re-sync periodically.

NEXT: our first look at Firefox 4, from July 2010 >>


The first beta of Mozilla's new Firefox 4 browser has some rough edges, but it's off to a good start.

Mozilla has released the first beta version of Firefox 4, its updated browser that offers new features such as a revised menu layout, more screen space for web pages and more HTML 5 HD video support.

Mozilla Firefox 4 Beta 1 is earning praise for some of its updates, such as its improved security and more HTML 5 functionality - Firefox 4 scored 198 out of 300 points on the HTML 5 test page - but not everyone is pleased. Mozilla is being criticised for borrowing features from competing browsers, including Chrome and Opera. Nevertheless, Firefox 4 still manages to put its own stamp on each new feature, and we expect regular Firefox users will be very happy with most of the changes found in Firefox 4.

Firefox Button

Firefox Button

For Windows 7 and Vista users, Mozilla Firefox 4 Beta 1 does away with the regular menu categories across the top of the browser window. Instead, menu items have been consolidated under a new button on the upper left hand side. Mozilla has also rearranged and removed some of the menu options used in previous version of Firefox. Menu options such as Edit, Tools, and Help are gone, and things like your toolbars, add-ons and layouts are now filed under the Customize menu. Some of the more redundant user options such as stop and reload are also gone since most users are more likely to use the new unified stop/reload button instead.

Mozilla Firefox 4 Beta 1 has also removed the downloads and private browsing options. However, you can still access both functions using their keyboard shortcuts: Ctrl, Shift, P for private browsing and Ctrl, J for downloads. If you don't like the new menu set up, you can get rid of the Firefox Button and switch back to traditional menus by clicking Firefox, Customize, Menu Bar.

Tabs on Top

Firefox 4 tabs

The Firefox Button works nicely with Mozilla Firefox 4 Beta 1's new tabs-on-top format to give you more screen space for viewing web pages. For now, tabs on top by default are only available for Windows users. But Mac OS X users can choose tabs on top as a layout option by right clicking on the toolbar. But we wouldn't recommend you try it as the tabs on top layout in OS X isn't very attractive, and Mozilla says this is going to improve in future beta versions.


The first beta of Mozilla's new Firefox 4 browser has some rough edges, but it's off to a good start.


Firefox 4 bookmarks

Your bookmarks have been moved from the regular menu to a standalone button on the right side of the browser. Despite the new look, the bookmarks button functions almost the same as previous versions. To bookmark a page, however, you click on the star icon found on the right side of Mozilla Firefox 4 Beta 1's address bar. Double clicking on the star icon will let you organise your bookmarks into folders and assign tags.

If you're using Mozilla Firefox 4 Beta 1's bookmarks option, consider downloading the Firefox Sync add-on to sync your Firefox bookmarks across multiple computers and user profiles.

Switch Tabs

Mozilla Firefox 4 Beta 1 offers a quick way to switch between multiple tabs through a search option in the Awesome Bar. Just place your cursor in the address bar and start typing the site or article name you're want to find. An option should read 'Switch to tab' under the page title; just select that option and Firefox will quickly move you to that tab. This new feature becomes really handy once you have 12 or more tabs open and is a great alternative to cycling through your tabs with the Ctrl, Tab keyboard shortcut.

If you're using Google Docs, you will want to be careful when using the switch tabs feature. At one point, we wanted to switch away from a Google Doc we had open and go to another tab, but we soon changed my mind and wanted to keep working on the document. Mozilla Firefox 4 Beta 1, however, wasn't too happy about our decision and wouldn't let us work on the document after we had entered text into the address bar. To get access to our document again, we had to switch to another open tab and then come back to our Google Docs page. Hopefully, this is just a bug and Mozilla will fix it before Firefox 4's official release.


Firefox 4 WebM

Mozilla Firefox 4 Beta 1 also brings support for WebM, Google's HTML5 video codec. For the most part, you probably won't have much occasion to use Firefox 4's WebM capability. But if you're interested, you can try it out by going to YouTube's HTML 5 page, and enrolling in the HTML 5 beta.

Overall, WebM is a serviceable codec, but we found WebM videos took a little longer to load than Flash versions. We also felt that sound quality in WebM was less than ideal, often having a very hollow feel with a lot of treble and little bass.

NEXT: our expert verdict >>

Mozilla Firefox 4: Specs

  • 233MHz processor
  • Windows 2000/XP/Server2003/Vista/7
  • 64MB RAM
  • 52MB hard-disk space
  • 233MHz processor
  • Windows 2000/XP/Server2003/Vista/7
  • 64MB RAM
  • 52MB hard-disk space


Mozilla Firefox 4 is a must-have upgrade if you're running Mozilla Firefox 3.x. If you've switched from Firefox to Chrome, however, Firefox 4 may not offer quite enough to lure you back, as many of the new features - at least on the user interface end--are clearly influenced by Chrome. But no matter what, it may be worth downloading and taking for a spin.

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