Firefox 4 Debuts Faster, More Secure Browser

March 24, 2011 § Leave a comment

Firefox 4 Debuts Faster, More Secure Browser

After 12 betas, 2 release candidates and over nine months of development, Mozilla today is officially releasing its next generation open source Firefox 4 web browser.

Firefox 4 is the first major browser update since Mozilla released Firefox 3.6 in January of 2010.

With Firefox 4, Mozilla developers have made multiple user facing changes that are very noticeable. Tabs are now on top of the address bar by default, instead of below as they have been ever since Firefox was first conceived. The user interface itself has been revamped in an effort to reduce clutter.

“We spent a bunch of time on the interface, making it as streamlined as possible, making it easy to get to the things that you want and also easy to get things out of your way” Johnathan Nightingale, director of Firefox at Mozilla “Moving from Firefox 3.6 to 4.0, we’ve compacted the interface, since most of the time users don’t need the whole menu.”

The ‘home’ button has been moved to the right of the address bar and the RSS icon has also been removed from the default display. Nightingale stressed that Mozilla has not taken any functionality away from the browser, they’ve just moved items from the default display in an effort to improve usability and efficiency.

Firefox 4 also integrates the Firefox Sync technology which enables users to synchronize their browser tabs and history across multiple systems. Firefox Sync extends to mobile platforms including Apple’s iOS by way of the Firefox Home application.


Another key aspect of usability is the new Panorama feature, which enables users to group tabs together. Tabs are also improved by way of the new App Tab feature which pins a tab to the left of the browser.

“App tabs is a recognition that the way people use the web today is different,” Nightingale said. “Something like Gmail is not simply a web page that a user opens then closes, it’s an application that happens to live on the web.”

Another tab improvement comes by way of a notification element. If something has changed within an app tab, in Firefox 4 there is now a blue glow that appears around the favicon. So for example if a user has a Gmail app tab, whenever new email is received the tab will now have a blue glow.


Mozilla’s extension system has also undergone a dramatic change for Firefox 4. The new browser makes use of the new Mozilla Jetpack platform which enables users to install and run extensions without the need to reload the browser.

For developers, Jetpack also makes it easier to build extensions by using JavaScript.

“You don’t have to learn XUL, you can just pull in some JavaScript APIs that feel a lot like web-based platforms,” Nightingale said.

Nightingale noted that extensions that were not built with Jetpack will still also run in Firefox 4. Mozilla’s add-ons site does identify which extensions require a restart and which ones do not.


On the security front, Firefox 4 includes Mozilla’s Do Not Track implementation. With Do Not Track, browser users are able to alert sites whether or not they want to be tracked. It is still up to the websites themselves however to actually support the specification or not.

Both Google Chrome and Microsoft’s IE 9 each have their own respective versions of a Do Not Track implementation.

There is also a new Content Security Policy feature in Firefox 4, which could potentially mitigate most of the risk associated with Cross Site Scripting (XSS) attacks.

“Content Security Policy lets sites say where they expect to be loading content from,” Nightingale explained. “So if script is loaded from somewhere else, it’s likely a XSS vulnerability on the website.”

Nighingale noted that CSP enables websites to block non-authorized JavaScript from running. Additionally the system can report unauthorized script usage as well.

“The reporting aspect means that every Firefox 4 users makes the web safer,” Nightingale said. “If a Firefox 4 user is the first one to see an un-authorized script, we’ll send back the ping and the site can see that and they can fix the bug.”

The other key new security features is HTTP Strict Transport Security (HSTS) which can force SSL security to be used. The HSTS feature is important as it can help users to be protected against potential credential sniffing attacks like the one propagated by Firesheep earlier this year.


Mozilla developers have also been determined to ensure that Firefox 4 is the fastest browser yet. Developers enhanced the JagerMonkey JavaScript engine in an effort to boost performance.

Having a fast browsing experience all begins with how fast the browser starts, which was also an area of improvement in Firefox 4.

“We’re not interested in optimizing for a specific benchmark, but we’re very interested in optimizing for common workloads,” Nightingale said.

Sean Michael Kerner is a senior editor at, the news service of, the network for technology professionals.


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