Firefox 3.5 released

By Stephen Withers
Wednesday, 01 July 2009 04:53

Open Source

As promised, Firefox 3.5 was released on June 30, bringing a healthy performance boost and new features to the widely used open-source browser.

Firefox 3.5 delivers a hefty list of new features, which explains the decision to use that version number rather than 3.1. (The previous version was 3.0.)

Improved speed is a theme of Firefox 3.5, with faster page rendering thanks to changes to the Gecko rendering engine, and faster JavaScript execution by the new TraceMonkey engine. According to Mozilla, the new version of Firefox is twice as fast as its predecessor.

TraceMonkey delivers better performance through just-in-time compilation, using the Trace Trees technique developed at the University of California, Irvine. The method is said to allow compilers to work more quickly and in less memory.

The default settings enable the new mode of operation for web page content but not for XUL (used in Firefox's user interface and to create extensions).

Among the improvements in Gecko is speculative parsing, a technique that allows faster rendering by not waiting for external scripts to load before continuing to process the HTML. One of the motivations for this development was the common use of external scripts for analytics and advertising purposes.

JSON (JavaScript Object Notation) is natively supported in Firefox 3.5, allowing much more rapid parsing of JSON objects while preventing malformed strings from triggering arbitrary code execution.

Firefox 3.5 also introduces web workers, an arrangement that allows a script to run in a separate background thread. Examples of the way this can be used include ensuring that processor-intensive tasks do not stop the user interface from being responsive, dividing complex tasks between multiple cores, and performing web I/O in the background.

Apart from the resulting speed, these features are generally hidden under the covers. So what might users actually notice in the way of new features?

Private Browsing is becoming a common feature in web browsers. Normally, a browser will retain a list of pages visited and other information about how it has been used. This can be convenient, but may not be appropriate when more than one person uses the same account. For example, the history could reveal the birthday gift you've ordered for a family member.

Please read on for more on Private Browsing and other new features of Firefox 3.5.