Internet Explorer 9 Guide for Developers

March 14, 2011

The Internet Explorer 9 Guide for Developers provides a look at the features and improvements in Internet Explorer 9. By using this guide, web developers and designers can take full advantage of these enhancements. Developers can also experience the platform in action using the Internet Explorer Test Drive.


Welcome to Windows Internet Explorer 9. As a developer, you want to know the latest information about the browsers you and your customers use. Internet Explorer 9 is the latest version of the world’s most popular web browser. We designed Internet Explorer 9 to help the web development community create rich, interoperable, standards-compliant web applications by providing the platform, tools, and features for the future web.

This document shows you, the web developer whose customers rely on Internet Explorer, how to use these new enhancements in your websites and applications. Be sure to check out the accompanying Test Drive site for a demonstration of these features in action. To offer feedback and see more information on what's new in Internet Explorer 9, see the Release Notes, as well as What's New in Internet Explorer 9 on MSDN. For the latest news about Internet Explorer 9, see the IE Team Blog. And as always, for the very latest developer information about Internet Explorer, visit the Internet Explorer Developer Center on MSDN.

Internet Explorer 9 is intended to help developers better understand how Internet Explorer 9 has progressed in the following dimensions of the platform:

  • All-around browser performance
  • Web standards support to help enable the same markup to work identically across different browsers
  • New graphics capabilities that harness the power of Windows PCs

All-around Browser Performance

Browser performance involves many different sub-systems within the browser. Different sites—and different activities within the same site—place different loads and demands on the browser. For instance, a web application like Windows Live Mail or Microsoft Office Web Apps exercises browser subsystems in completely different ways than a news aggregation site like Bing News or Digg.

Introducing “Chakra”, the New JavaScript Engine

Script engine performance is just one part of the overall browser performance picture. Script performance in Internet Explorer 8 improved exponentially over that of Internet Explorer 7, and “Chakra”, the new JavaScript engine in Internet Explorer 9, does it again. The Chakra engine interprets, compiles, and executes code in parallel and takes advantage of multiple CPU cores, when available. For more details, see "The New JavaScript Engine in Internet Explorer 9" on the IE Team Blog.

Of course, the Internet Explorer team is looking at the performance characteristics of all the browser’s subsystems as real-world sites use them. The goal is to deliver better performance across the board for real-world sites—not just benchmarks.

Web Standards Support for Same Markup

Internet Explorer provides rich, interoperable capabilities to web developers. The Internet Explorer Team knows you don’t want to rewrite and retest your websites again and again; standards adoption by browser vendors is a good way to reach that objective.

With Internet Explorer 8, the Internet Explorer team delivered a highly interoperable implementation of CSS 2.1, and concurrently contributed a test suite with over 7200 tests to the World Wide Web Consortium (W3C). This is important. Without validation tests, standards are more challenging to implement consistently, thereby making them difficult for site developers to rely on.

Internet Explorer 9 makes significant investments in standards support and interoperability. For instance, new HTML5 support, better support for a number of CSS3 features, and—a first for Internet Explorer—built-in support for SVG are all part of Internet Explorer 9.

New Graphics Capabilities that Harness the Power of Windows-based PCs

The Windows ecosystem provides amazing hardware innovation. With Internet Explorer 9, web developers can now take advantage of that innovation with hardware-driven rendering of graphics and text.

Internet Explorer 9 uses the DirectX family of Windows application programming interfaces (APIs) to enable several advances for web developers. We have moved all graphics and text rendering from the CPU to the graphics card by using Direct2D and DirectWrite. Graphics hardware acceleration means that rich, graphically intensive sites can render faster on Windows while using less CPU power. Plus, you can take advantage of these changes automatically while you author sites with the same standards you are used to.

Improved Interoperability Through Standards Support

Important   The new standards support in Internet Explorer 9 requires the browser to be in Internet Explorer 9 Standards mode (“IE9 mode”). The best way to do this is to use a standards !DOCTYPE directive and no X-UA-Compatible meta tag or HTTP header. The !DOCTYPE to invoke IE9 mode is the following:

<!DOCTYPE html>

Of course, you can use the !DOCTYPE and X-UA-Compatible meta tag or HTTP header to change the default as you see fit.

To determine the current document mode, press F12 to open the Internet Explorer developer tools, and then look on the right side of the menu bar. To override the document mode, on the Document Mode menu, click Internet Explorer 9 Standards.

See the Platform Versioning section of this guide for updates about document mode behaviors in Internet Explorer 9.

List of New Features

For your convenience, this list contains all the new developer features in Internet Explorer 9. For information about changes from prerelease builds of Internet Explorer 9, see Revision History.

Enhanced CSS3 support
  • Rounded corners via the border-radius property
  • CSS3 background and border features
  • The opacity property
  • RGBA, HSL, and HSLA color models
  • CSS3 fonts properties and new web font formats
  • CSS3 media queries
  • CSS3 namespaces
  • CSS3 values and units
  • CSS3 selectors
Improved data URI support Document Object Model (DOM) Improvements Enhanced DOM capabilities Parsing and serializing XML to and from the DOM New DOM Level 2 (L2) and Level 3 (L3) support and updated behaviors
  • DOM Core (L2, L3) and Views (L2)
  • DOM Element Traversal
  • DOM Events (L2, L3)
  • DOM L2 Style
  • DOM L2 Traversal and Range
New whitespace handling behavior ECMAScript feature enhancements Added HTML5 support
  • Geolocation
  • The video and audio elements
  • The canvas element
  • The Selection interface
  • Improved parsing of HTML elements
  • Text selection APIs
ICC v2 and v4 color profile support on images New Selectors API Level 2 support for the msMatchesSelector method SVG features
  • Basic shapes: rectangles, circles, ellipses, lines, polylines, and polygons
  • Clipping, masking, and compositing
  • Coordinate systems, transforms, and units
  • Document structure, metadata, and extensibility functionality
  • Gradients and patterns
  • Interactivity
  • Linking and views
  • Painting and color
  • Paths, including full capabilities of the path element and d attribute
  • Text
Additional platform versioning capabilities
  • Pinned sites
  • New document mode
  • New user-agent (UA) string
Developer Tools additions
  • Performance improvements
  • Console tab
  • Network tab
  • UA switcher tool
  • Real-world performance measurement

Revision History

March 16, 2010: Created for Internet Explorer Platform Preview.

April 15, 2010: Updated with information about:

  • CSS3 Namespaces Module support
  • Additional CSS3 selectors support
  • More DOM support details
  • More SVG support details, including embedding limitations
  • ICC color profiles support

May 5, 2010: Updated for Internet Explorer Platform Preview Build 2 with information about:

  • More DOM support details
  • New DOM features:
    • New DOM Core APIs
    • DOM HTML
    • DOM Traversal
    • New DOM L3 events:
      • DOMAttrModified event
      • DOMContentLoaded event
      • Composition events
  • New user-agent (UA) string
  • Data URI changes
  • Developer tools additions: Console tab and UA switcher tool

June 23, 2010: Updated for Internet Explorer Platform Preview Build 3 with information about:

  • New CSS3 features:
    • New background and border features
    • HSL and HSLA color models
    • CSS3 Fonts support
    • CSS3 Values and Units support
    • New display property values
  • New DOM Element Traversal support
  • New HTML5 features:
    • video, audio, and canvas elements
    • Selection interface
  • New Selectors API Level 2 support:
    • matchesSelector method
  • New SVG features:
    • Clipping, masking, and compositing
    • Gradients and patterns
    • Interactivity
    • Linking and views
    • Painting and color
    • Text

August 4, 2010: Updated for Internet Explorer Platform Preview Build 4 with information about:

  • “Chakra”, the new JavaScript engine
  • Enhanced DOM capabilities
  • New support for the WebIDL specification
  • The window.msPerformance object
  • Fleshed out canvas section with links to examples

September 15, 2010: Updated for Internet Explorer 9 Beta with new links and information about:

  • DOMParser and XMLSerializer
  • Pinned Sites

October 28, 2010: Updated for Internet Explorer Platform Preview Build 6 with information about:

  • CSS 2D Transforms
  • HTML5 Semantic Elements
  • Fixed supported ICC color profiles version number

February 10, 2011: Updated for Internet Explorer 9 Release Candidate with information about:

  • HTML5 Geolocation
  • Pinned Sites (updated)
  • Compatibility Mode (updated)
  • Other miscellaneous document fixes

February 18, 2011: Updated with additional information about:

  • Pinned Sites
  • HTML5 Canvas

March 14, 2011: Updated for Internet Explorer 9 (RTW):

  • updated version text
  • ECMAScript 5 (added links)