Firefox 9 Aurora Comes with Faster JavaScript, More Under-the-Hood Tune-Ups

With Firefox 9 Aurora, Mozilla has wrapped up this set of updates, coming after Firefox 7 stable and Firefox 8 Beta. Firefox 9 promises to be an interesting release, but, as per usual, the new features and changes are not huge, unless you're an Android tablet user.

Most of the changes are under the hood, but Firefox 9 should feel faster and snappier than previous releases. Memory usage has been further improved, following the big update in Firefox 7 and continued efforts in Firefox 8.

"The latest Firefox Aurora for Android has lots of exciting new experimental features that make browsing simpler and more intuitive, especially on tablets," Mozilla summarized.

"This update also includes technologies that will help developers create more interactive websites and apps," it said.

New Android tablet UI

Firefox 9 Aurora, is the first release to feature the new tablet interface for the Android builds. We've previewed the new UI earlier and it landed in the developer versions a few weeks back.

Now, more adventurous users running the Aurora channel can see it in action for themselves.

On the desktop front, most changes are under the hood, but they're pretty interesting nonetheless.

Type inferring for JavaScript leads to better performance

Firefox 9 introduces a new trick for improving JavaScript performance, Type Inference. If you're not a programmer, you're probably not familiar with the term.

In JavaScript, the type of the variables is not declared, usually, first hand, rather, it's detected at run time. This adds great flexibility to the language, but it also means more overhead.

Type Inference, as the name implies, tries to determine the type of the variable from the get go, leaving the Firefox JavaScript engine to do other things and use resources more efficiently.

Because of the change, Firefox 9 handles JavaScript better and the performance improvements can be seen in benchmarks like Mozilla's Kraken or Google's V8 but also in the real-world.

Check for Do Not Track option via JavaScript

Firefox 4 introduced the Do Not Track header. This enabled users to 'tell' websites that they don't want to be tracked by advertisers, building a user profile on them.

With Firefox 9, developers can check to see if a user has enabled the feature via JavaScript as well.

Chunked XHR

Another thing that should speed up websites, provided developers implement it, is support for chunking XMLHttpRequest (XHR). This way, data can be displayed and used by websites as soon as it starts arriving, before the full download has completed.

Firefox for Windows is available for download here.
Firefox for Linux is available for download here.
Firefox for Mac is available for download here.