The preview can be downloaded at Microsoft's IE test drive page here. However, the release is not a complete Web browser and it only works with Windows 7 or Windows Vista Service Pack 2 (on both x86- or x64-based PCs), according to the release notes. Platform preview 3 can be run alongside IE 8 without conflict and will overwrite any earlier installed IE 9 platform preview, according to Microsoft.
Microsoft is trying something a little different with its platform preview releases of IE 9. The releases are more like pre-alpha demos for developers that show performance and feature improvements of the browser. Microsoft officials have said that IE 9 testers can expect to see a new platform preview every eight weeks or so, but platform preview 3 arrived about two weeks early. The last release came in early May.
Platform preview 3 continues Microsoft's focus on supporting Worldwide Web Consortium (W3C) specifications, such as the developing HTML 5 and CSS 3 specs. It also includes some improved benchmark scores for JavaScript performance. With this release, Microsoft added support for the Web Open Font Format (WOFF) through CSS3. IE 9 uses WOFF, the underlying hardware and Windows DirectWrite (a DirectX API) to produce high-quality font rendering.
For those developers worrying about supporting legacy Web apps based on IE 6, Microsoft announced earlier this month that IE 9 will be capable of supporting IE 6 quirks mode through the use of conditional comments. Otherwise, Microsoft generally recommends that Web developers should avoid conditional comments altogether and use HTML 5 feature detection in their code.
In an IE blog post on "IE's Compatibility Features for Site Developers," Microsoft Program Manager Marc Silbey explained the point: "There is one case where it is appropriate to use Conditional Comments, which is for backward compatibility with IE6 or IE7 stylesheets."
Platform preview 3 includes native support for the video and audio elements in the HTML 5 spec ( and tags), as well as native support for the canvas element ( tag). Developers can use these tags to embed video and audio in their Web sites without users having to have a plug-in (such as Adobe's Flash) installed in their browsers to enable playback. Microsoft provides a video describing native video and audio support in IE 9 here, as well as an overview of the new IE 9 demos here.
The addition of the canvas element is new with platform preview 3, whereas support for the other two elements had been announced in March. The canvas element provides a compact way to write animations in Web sites or rich Internet applications. A short Microsoft-produced demo showing how the canvas element is supported by IE 9 is available here. There's also a video on Amazon.com's use of the canvas tag.
Microsoft has improved ECMA-262 Fifth Edition standards support in IE 9's "Chakra" JavaScript engine. Platform preview 3 includes support for "new array and object methods, as well as other language enhancements for working with strings and dates," according to Microsoft's announcement. A short video on IE 9's use of ECMAScript 5 standards is available here.
Microsoft also reported improved benchmark test results with platform preview 3. A chart in Microsoft's announcement shows that IE 9 nearly equals the performance of Safari, Opera and Chrome for the fastest performance on a WebKit SunSpider JavaScript benchmark test. Similarly, Microsoft's IE 9 now scores 83 of 100 point in the Acid3 test, up from 68 of 100 points in the last platform preview. (Microsoft tends to downplay Acid3, saying that it doesn't test the most used features in browsers.)
In building IE 9 with an eye toward W3C standards from the ground up, Microsoft hopes to help Web developers write code once that will be supported across all other browsers. Microsoft's concept of targeted W3C standards includes HTML 5, as well as "SVG 1.1 2nd Edition, CSS3, DOM L2 and L3, and ECMAScript 5," according to Jason Upton, test manager for Internet Explorer.
The main issue for Microsoft and other browser makers is that the W3C specs are interpreted differently. Browsers also use different rendering engines, but even browsers using the same engine (such as the WebKit engine in Apple's Safari and Google's Chrome browsers) have shown varying HTML 5 test results. Consequently, Microsoft has been submitting a series of tests of the HTML 5 spec to W3C working groups. On Wednesday, Microsoft announced that it had submitted 118 new tests to the W3C, bringing the total to more than 1,600 tests. It has also written 1,309 JavaScript test cases and plans to make them available to Web developers.
Microsoft is claiming that IE 9 is the first browser demonstrating speed and performance advantages by tapping into the power of graphics processing units (GPUs) in devices. This capability is part of HTML 5's planned support for scalable vector graphics (via the SVG 1.1 spec).
Next year, Microsoft's chip-producing partner, AMD, plans to roll out its new Fusion family of accelerated graphics processors that will combine GPU and CPU capabilities. A demo of IE 9 using AMD's Fusion processors is shown in this blog post. The blog also shows how Microsoft PowerPoint 2010 enables hardware-accelerated graphics by default. Such support is becoming a general trend for software developers, according to the blog.
Microsoft Releases IE 9 Preview 2
