The last time I reviewed a major new version of Firefox, it was June 2008 and Mozilla had just delivered Firefox 3. Back then, I was a diehard Firefox user and advocate, and had been using the product since it was an early alpha browser called Phoenix.

A lot has changed since then. Firefox's position as the browser of choice for technophiles and others in the know has been usurped, in dramatic and unexpected form, by Google Chrome. And Firefox's seemingly unstoppable usage share climb actually did stop: It's essentially been stagnant for the past year or so.

Since Firefox 3, Mozilla evolved its browser, but perhaps too slowly. There was a semi-major release, Firefox 3.5, and then a Firefox 3.6 release as well. But Firefox 4 has been years in the making and it enters a market that is no longer quite so friendly. It should see rapid adoption, sure, but the question is whether Firefiox 4 can reverse the stagnation and get the product on a growth path again.

Mozilla, for its part, promises to speed up Firefox development going forward. And a big part of that strategy involves not focusing on these big bang releases for the foreseeable future. It's a good idea, one that comes from Chrome, actually, one that Microsoft is itself co-opting for Internet Explorer. But that's in the future.

What's new in Firefox 4

Slow product development aside, Firefox 4 is indeed a major reimaging of the Firefox web browser and is much more attractive and usable than previous versions, especially under a modern OS like Windows 7. In keeping with other recent browser releases--IE 9 and Chrome 10/11--Firefox 4 offers an enhanced JavaScript rendering engine, of course, and better performance, with just enough hardware acceleration to be included in the same conversation as those other browsers. Firefox has always had excellent web standards support, and that's as expected. What I'm more concerned with, I guess, is the day to day stuff. I use Chrome and IE 9 regularly. What does Firefox 4 bring to the table today? Is it enough to deflect interest in IE 9 and Chrome?

Here's what's new in this release.

Streamlined new user interface. Firefox 4 takes Mozilla's browser in a decidedly new and more attractive direction, in contrast to the ugly mistake that was the previous two versions. Now, the browser tabs are aligned across the top of the browser window, as they are in Chrome, and the menu bar is hidden by default, though much of that functionality is replaced by a nice new Firefox button we'll get to in a bit.

The redesigned default toolbar is mostly a success, with attractive buttons and other controls, but I take exception to the IE-like weirdness of moving the Home button way over to the right side of the screen; navigation buttons should all be together, on the left.

In Firefox's defense, you can at least change the button's location, unlike in IE. In fact, this level of customization remains a key strength: It is more customizable than Chrome, and far more customizable than IE. And you can drag toolbar buttons onto the tab bar if you want, too. Which is just excellent.

Unlike other modern browsers, Firefox 4 does not combine the address bar (immaturely called the "Awesome bar") with the search box, but instead leaves them as separate screen-stealing entities. Yes, you can awkwardly launch searches from the address bar if you want. But these features should be combined.

Tabs improvements. Aside from moving the tabs to the top of the window, which I like, Mozilla has improved the tabbed browsing experience in other ways. The biggest is a new feature called App Tabs, which gives Firefox a replacement, of sorts, for the application shortcut functionality in Chrome and IE 9. I say "sort of" here, because it's not exactly the same. In fact, it looks and works a lot like a similar feature in Chrome OS: You can right-click on a tab (for say Gmail, Google Calendar, or other often-visited sites you leave open all day) and choose Pin As App Tab. This creates a new, smaller tab at the left of the tab bar. And all pinned tabs will open every time you open Firefox for the first time. (Subsequent Firefox windows will not include these pinned App Tabs.)

The problem, of course, is that while App Tabs are handy, the standalone window approach used by Chrome and IE 9 is superior, because these browsers treat your favorite web sites and apps like local Windows applications, each with its own window. And that means Gmail works in the same way I think of it, as its own app. Just not in Firefox.

Firefox button. As with other browsers that have removed the menu bar for a cleaner look, Firefox overloads a UI button, in this case the new Firefox button, with a number of commands you'd previously have to scroll around menus to find. Presented as an orange button about the same size and shape as the window buttons (Minimize, Maximize/Restore, and Close), but on the left side of the window, the Firefox button is an obvious target and doesn't look too horrible.

In the menu, you'll find often-needed commands like Print, Save Page As, and Full Screen, as well as jumping off points to important browser functionality such as Bookmarks, History, Downloads, Add-ons, Options, and Help.

Note that you can still bring up the classic Firefox menu temporarily by tapping the ALT key.

Panorama. All browsers deal with tab and window management in different ways, and Firefox has had tab grouping for a while now. In Firefox 4, Mozilla adds a new bit of functionality to this feature via a new Panorama UI that lets you drag and drop open tabs, visually, into groups which you can name. So you can group tabs according to the tasks you wish to perform and then easily re-open all those tabs later if desired.

This kind of micromanagement will appeal to some people, I guess, but it seems like overkill to me. And not a little bit like the Expose and Workspaces features from Mac OS X.

Add-on Manager. Whereas the previous few Firefox versions were saddled with a curious-looking Add-on Manager that was relic from a Windows Vista-inspired design sidetrip that never materialized into anything, Firefox 4 includes an all new Add-on Manager that's attractive and efficient. From this simple interface, which takes up the entire browser window (a la Chrome), you can manage your browser add-ons, find new add-ons (now an inline feature that doesn't open a separate browser window like before), manage extensions, manage the theme and/or persona (sort of a Firefox-specific "super theme"), and manage plugins.

Firefox's extensibility is, of course, one of the best reasons to choose this browser. But one of the things Mozilla still isn't all that good about is backwards compatibility: Many of the add-ons I want to use--like Readability, notably--aren't yet compatible with Firefox 4, and it refuses to install the older version. This will get better over time, at least with currently supported add-ons.

Firefox Sync. Chrome offers incredible sync capabilities, tied to your Google account, and it's nearly flawless, with syncing of web apps, autofill, bookmarks, extensions, passwords, preferences, and themes. IE 9 offers nothing like this natively, but there are some (pretty weak) ways to at least sync IE Favorites from PC to PC, such as with Windows Live Mesh. Thankfully, Firefox is going the Chrome route with a more complete solution. But the way Mozilla has implemented this feature borders on the ludicrous.

So yes, you get some useful item synched, include history, bookmarks, passwords, and even open tabs. And yes, it's tied to an account, in this case what's called a Firefox Sync Account, which you can create easily enough.

The problem is you can't just sign in with your user name and password. Instead, you must also keep track of a lengthy Sync Key. And if you do something like I have--install Firefox, create the account, then wipe out the computer and not back up that key--you have to logon, generate another Sync Key, and What the what?? If you can do that, why do you need a Sync key at all?

Oh wait, I forget the best part. Generating a new Sync Key wipes out all of the data stored with your account. So you can do this, but then you lose everything.

This system is simply broken. It makes no sense at all.

Performance. As I've noted in the past, all modern browsers are pretty darn fast, and certainly Firefox holds it own in day to day use. Mozilla, like Google and Microsoft, points to certain benchmarks and other tests that prove the prowess of the product. It claims Firefox 4 is up to six times faster than its predecessor, too, with improved startup and page load times.

And like IE 9 in particular, Firefox was released concurrently with a web site, Web o' Wonder, designed to cast the browser in the best possible light. It's full of demos, like the IE 9 Beauty of the Web site, and it gets bonus points for providing demos that don't work at all, or work slowly, in other browsers. Cute!

I will say this. While Firefox offers some hardware acceleration, it's not full hardware acceleration like you get in IE 9. On the other hand, Firefox is inarguably more standards compliant than IE 9, though Microsoft would probably argue that its browser does better with the web technologies developers are actually using. Like the Cold War, it's an ongoing arms escalation. Today's winner may be tomorrow's loser.

So rather than try to come up with some pithy statement about Firefox 4 performance, I'll just fall back on my original premise: All modern browsers are pretty darn fast. And Firefox 4 is a modern browser. I haven't seen anything here to suggest its well ahead--or well behind--the competition in normal, day to day browsing. Remember, Benchmarks and demos are just like statistics: They show you exactly what their creators intend to show you.

Privacy. Also in keeping with recent browser trends, Firefox 4 implements a form of the Do Not Track functionality that the Federal Trade Commission recently called for. Put simply, Microsoft's implementation, called Tracking Protection in IE 9, is superior. And that's because Mozilla has done the absolute minimum here, by implementing Do Not Track as an opt-in system for web site. So in Firefox, you have to find the single checkbox that enables the feature--Firefox Button, Options, Advanced, "Tell web sites I do not want to be tracked"--and just hope for the best. Please.

Final thoughts

I like Firefox 4 a lot, but at this point in time, I already have two very strong contenders that I'm using regularly, Internet Explorer 9 and Chrome. But don't take that the wrong way: I could use Firefox 4 without feeling like I was compromising in some way, and that most definitely wasn't the case with the past few Firefox 3.x releases. If you are already using Firefox, the new version is a no brainer, though you might need a bit of time to get used to the new UI, if you haven't already been playing with the beta. Don't worry, it's worth it, and much nicer, ultimately, than the old UI.

If Mozilla does come through on its promise to add features more rapidly to Firefox over time, they could have a compelling alternative on their hands again, and viable competition to both IE 9 and Chrome. Certainly, Firefox 4 is a great foundation. Recommended.