Windows 8, plugin-free browsing, and UA spoofing

Microsoft released a developer preview of Windows 8 at this week’s BUILD conference including a preview release of the next version of Internet Explorer. Windows 8 will include a “Metro style browser,” a simplified appliance-like view based on Windows Phone tiles. The Metro interface is powered by Internet Explorer (Trident, Chakra) behind-the-scenes in a special “immersive” full-screen runtime without support for browser plugins such as Adobe Flash Player. Microsoft is bundling a special compatibility view list with a uaStringImmersive attribute to spoof an iPhone, iPad, or even Firefox User-Agent to trigger special views on websites designed for a plugin-free or full-screen experience.

<iecompatlistdescription>

  <domain featureSwitch="createElementWithMarkup:false">youtube.com</domain>

  <domain uaStringImmersive="Firefox 5">tv.slashgear.com</domain>

  <domain uaStringImmersive="iPad">mashable.com</domain>

</iecompatlistdescription>

Sites using feature detection at runtime helps avoid assuming the same features for desktop Internet Explorer and Metro’s “immersive” Internet Explorer. The application/x-shockwave-flash handlers present in one version of the browser may not be present in the next. Assuming Internet Explorer cannot handle XMLHttpRequest or display H.264 video with AAC audio inside a <video> could land your hostname in the Compatibility View penalty box.

The Internet Explorer 9 compatibility view list is available online in eXtended Markup Language (XML) format including existing featureSwitch handlers.

Feature detect at runtime or update your content negotiation User-Agent matchers for Internet Explorer 10 before Microsoft decides to spoof its User-Agent for iPad treatment.