Microsoft has introduced the second Platform Preview of Internet Explorer 9, aimed at giving developers an idea of what is coming in the next version of the web browser.
The preview update released on Wednesday keeps to Microsoft's promise to deliver a developer refresh every eight weeks until it puts out a public beta. The final release of IE9 looks likely to be some way off, given that the company has not outlined a timeline for its delivery.
The second Platform Preview adds support for two frequently used APIs, and Microsoft's test drive site for the browser now includes more samples. The samples showcase the way the preview implements HTML 5 standard markup with scrolling text, animated icons that appear as the mouse is moved over a grid and an animated thumbnail grid of images loaded from Flickr.
Dean Hachamovitch, Microsoft's general manager for Internet Explorer, explained why the update still has the same minimal user interface as the first version.
"This preview continues to be a platform preview," Hachamovitch told ZDNet UK, emphasising that Microsoft does not expect users to do general web browsing with it. "This is the least possible wrapping around the browser that enables developers to use it on their sites and to test them."
"We got faster and the graph [of results] is now a very tight cluster. We're down to millisecond differences," he said.
In what he described as a side effect of other work, the preview's score on the Acid3 test of web standard compliance goes up from 55 to 68. "As we improve support for the markup developers actually use, the Acid scores will go up," Hachamovitch added.
The first IE9 Platform Preview introduced support for two APIs — addEventListener and getComputedStyle — used on many websites that were not supported in IE8. The second preview supports another two frequently-used APIs: characterSet and getElementsByClassName. There are also improvements to page layout and to IE9's vector graphics support.
Future previews will add more features. HTML 5 video tag support will come in Platform Preview 3 (due in another eight weeks), Hachamovitch said. He also confirmed that this will support only the H.264 video codec, although Flash and Silverlight plug-ins and links to external media players allow sites to use other codecs.
One significant reason for supporting H.264 solely — apart from issues to do with IP and patents — is the widespread availability of hardware acceleration for that codec, Hachamovitch said.
"There's this challenge with saying, 'we'll invent a new video thing'. One: is there something very new? Does it pass the lawyerly test? And then, having dedicated hardware that can play this codec makes a huge difference in battery life and performance. Look at the promise of HTML 5 apps; do you really want another codec in there that will slow the whole system down?" he said.
Microsoft's test- and data-driven approach to IE9 development may help other browsers, as it also announced on Wednesday that it has added 79 new tests to the HTML 5 compliance test suite that it is donating to the World Wide Web Consortium.