Firefox 5 focuses on security and privacy

Firefox 5 is now available to download just three months after the launch of Firefox 4, bringing with it improvements such as the addition of a do-not-track feature for the Android version of the browser.

Firefox 5 makes it easier to find the do-not-track option in user preferences. Screengrab: Stephen Shankland

The release is the first on the accelerated release cycle, meaning Mozilla plans to deliver a new full version of the browser every three months. The company says this allows it to deliver performance, security and stability tweaks more quickly. Google also delivers full version updates to its Chrome browser every six weeks, but does so automatically rather than requiring a manual upgrade.

This release adds support for more modern web technologies that make it easier for developers to build amazing Firefox add-ons, web applications and websites.

– Mozilla

"The new version of Firefox comes on the heels of the wildly successful release of Firefox 4, which had more than 200 million downloads on Windows, Mac and Linux," Mozilla said in a blog post on Tuesday. "This release adds support for more modern web technologies that make it easier for developers to build amazing Firefox add-ons, web applications and websites."

Previous versions of Firefox had continually missed their projected release dates. For example, Firefox 4 missed both its initial target date of October 2010 and its revised release date of February. It was eventually released on 22 March.

Among the feature set of Firefox 5 is added support for CSS animations, improved JavaScript, memory and networking performance, and improved standards support for HTML 5, XHR, MathML, SMIL and Canvas.

Do not track

However, the most notable change is the relocation of the 'Do Not Track' option to make it easier to find in the preferences section. The feature was introduced with Firefox 4 and allows users to specify whether they want their browsing data to be passed to third-party advertisers.

In contrast to other browsers with similar privacy features, Mozilla's Do Not Track relies on the header information being relayed to advertising companies, who can choose whether or not to honour the request not to collect data. This feature has also now been added to the Android version of Firefox.

Internet Explorer 9 (IE9) has a similar privacy feature, but instead of relying on requests it uses a tracking protection list (TPL) — essentially a blocklist to decide which third-party elements of a web page to block or allow. Also unlike IE9, Firefox 5 will run on Windows XP machines.

As well as improving stability and fixing bugs — such as a long-standing idle connection bug — Firefox 5 also rectifies a number of security issues, including two related to the WebGL graphics technology. Five of the holes were marked as critical, meaning the weakness could be exploited by an attacker without any user interaction beyond normal browsing behaviour.

Add-on SDK

Also on Tuesday, Mozilla launched an add-on software development kit (SDK) and a beta of the Builder hosted online environment, which the company said makes it quick and easy to build add-ons for the browser.

"If you're familiar with JavaScript, HTML and CSS, then you already have the necessary skills to build add-ons using these tools. In addition, all add-ons created with the Add-on Builder or Add-on SDK are restartless by default, meaning users do not have to interrupt their browsing to begin using your add-on right away," Mozilla said in a blog post.

The SDK is aimed at people who want to work on a local machine using a command-line interface and their own development environment, while Add-on Builder is a hosted, online environment that includes tools such as a code editor, module selection and testing features.