The main feature of this release is out-of-process plugins: on Windows and
Linux, plugins such as Flash and Silverlight run in a separate process from
the browser. If a plugin crashes it will not crash the browser, and
unresponsive plugins are automatically restarted. (Note that we are working
on this for Macs as well, but is not part of this preview release.) We are
making this preview release available so that it can get wider testing and
* We’ve removed link history lookup from the main thread and made it
asynchronous. This results in less I/O during page loads and improves
overall browser responsiveness.
* Loading the HTML5 spec no longer causes very long browser pauses.
* A large number of layout performance improvements have been made,
including work around DOM access times, color management performance,
text area improvements and many other hot spots in the layout engine.
improved, faster closures, some support for recursion in TraceMonkey to
name a few.
* Improvements to the performance of repainting HTML in <foreignObject>.
* Strings are not copied between the main DOM code and web workers,
of data between threads.
Web Developer Features
* Support for Content Security Policy. This is largely complete, minus the
ability to disable eval().
* The placeholder attribute for <input/> and <textarea> is now supported.
* Support for SMIL Animation in SVG. Support for animating some SVG
attributes is still under development and the animateMotion element
isn’t supported yet.
* Support for CSS Transitions. This support is not quite complete: support
for animation of transforms and gradients has not yet been implemented.
* Support for WebGL, which is disabled by default but can be enabled by
changing a preference. See this blog post and this blog post for more
* Support for the getClientRects and getBoundingClientRect methods on
Range objects. See bug 396392 for details.
* Support for the setCapture and releaseCapture methods on DOM elements.
See bug 503943 for details.
* Support for the HTML5 History.pushState() and History.replaceState()
methods and the popstate event. See bug 500328 for details.
* Support for the -moz-image-rect() value for background-image. See bug
113577 for more details.
Please note that this release intended for developers and testers. Mozilla
encourages web developers to test this developer preview against their web
sites and file bugs on any problems.
For more information, including a complete list of new features, see the
release notes, as well as the “Upcoming Firefox feature for developers”
article on the Mozilla Developer Center.
Download and information links are available on the Mozilla Developer Center