After loads of beta releases (12 to be precise), Mozilla has finally released a Release Candidate version of Firefox 4 yesterday (March 9). Hopefully we will soon have the final version of Firefox 4 unless there is no more Release Candidate (RC) version before the final release.

What Firefox 4 RC is All about:

  • Firefox 4 RC is available in 79 languages
  • Support for the proposed Do Not Track (“DNT”) header
  • Connection status messages are now shown in a small overlay
  • WebGL is enabled on all platforms, but, like for other hardware acceleration features, many buggy drivers or driver versions are blocked
  • The default homepage design has been refreshed
  • Firefox no longer switches into offline mode automatically
  • Overhaul of the bookmarks and history code, enabling faster bookmarking and startup performance
  • Per-compartment garbage collection is now enabled, reducing work done during complex animations
  • The Firefox Sync setup experience has been greatly improved across desktop and mobile devices
  • Additional polish for the Firefox Add-ons Manager
  • Uses JägerMonkey, a new, faster JavaScript engine
  • Certain rendering operations are now hardware-accelerated using Direct3D 9 on Windows XP, Direct3D 10 on Windows Vista and 7, and OpenGL on Mac OS X
  • Improved web typography using OpenType with support for ligatures, kerning and font variants
  • HTML5 Forms API makes web based forms easier to implement and validate
  • Support for the new proposed Audio Data API
  • Direct2D Hardware Acceleration is now on by default for Windows 7 users
  • Firefox button has a new look for Windows Vista and Windows 7 users
  • Support for HSTS security protocol allowing sites to insist that they only be loaded over SSL
  • Firefox Sync is now included by default
  • A new feature gives users a visual overview of all open tabs, allowing them to be sorted and grouped
  • An experimental API is included to provide more efficient Javascript animations
  • Firefox now supports the HTML5 video “buffered” property
  • Tabs are now on top by default on Windows, Mac OS X, and Linux
  • You can turn any tab into an “App Tab” by right-clicking on it and selecting “Make into App Tab” from the context menu
  • Web developers can animate content using CSS Transitions
  • Responsiveness and scrolling improvements from the new retained layers layout system
  • JavaScript speed improvements due to engine optimizations
  • Changes to how XPCOM components are registered in order to help startup time and process separation
  • You can search for and switch to already open tabs in the Smart Location Bar
  • New Addons Manager and extension management API (UI will be changed before final release)
  • Significant API improvements are available for JS-ctypes, a foreign function interface for extensions
  • The stop and reload buttons have been merged into a single button on Windows, Mac OS X, and Linux
  • The Bookmarks Toolbar has been replaced with a Bookmarks Button by default (you can switch it back if you’d like)
  • Crash protection for Windows, Linux, and Mac OS X when there is a crash in the Adobe Flash, Apple Quicktime or Microsoft Silverlight plugins
  • CSS Transitions are partially supported
  • Full WebGL support is included
  • Core Animation rendering model for plugins on Mac OS X. Plugins which also support this rendering model can now draw faster and more efficiently
  • Native support for the HD HTML5 WebM video format
  • Web developers can update the URL field without reloading the page using HTML History APIs
  • More responsive page rendering using lazy frame construction
  • Link history lookup is done asynchronously to provide better responsiveness during pageload
  • CSS :visited selectors have been changed to block websites from being able to check a user’s browsing history
  • New HTML5 parser
  • Support for more HTML5 form controls
  • Web authors can now get touch events from Firefox users on Windows 7 machines
  • A new way of representing values in JavaScript that allows Firefox to execute heavy, numeric code (used for things like graphics and animations) more efficiently

One of major improvements that Firefox 4 brings compared to previous versions is huge performance enhancements, including brand new JägerMonkey JavaScript engine. From faster start up times and graphics rendering to improved page load speed.

Via: [Firefox 4 RC Features and Firefox 4 Release notes]