Websites that are designed for older versions of Windows Internet Explorer don't always display as expected in the current version. We addressed this in Windows Internet Explorer 8 by adding the Compatibility View function that allows users to "revert" to a previous browser version of the platform, which emulates IE7 Standards mode.

Examples of incompatibility issues that are addressed by Compatibility View include incorrect browser or feature detection. Today many sites use browser detection instead of feature and behavior detection to give Internet Explorer markup that is not interoperable with IE9 Standards mode or with other browsers. This can result in major functionality breaks on sites rendered in IE9 mode.

Compatibility View allows content designed for older web browsers to render well in newer versions of Windows Internet Explorer 9. The Compatibility View (CV) List automatically displays the content of websites in Compatibility View without further interaction. Internet Explorer 9 includes support for compatible document modes and a CV List that is similar to that shipped with Internet Explorer 8.

Tool Description

We only add a site to the Compatibility View List when the site:

  • Is designed to run in an older version of Internet Explorer
  • Doesn't run well in IE9 mode
  • Doesn't declare an "X-UA-Compatible " meta tag or header

Compatibility View now addresses both feature detection and conditional comments.

Feature Switches: To keep sites working well in IE9 mode instead of reverting to IE8 Standards mode or IE7 mode, the Internet Explorer 9 CV List includes a new capability called a "featureSwitch." This makes specific APIs in IE9 mode behave as they do in previous Internet Explorer versions.

We intend to remove feature switches as soon as developers update their sites to use the same markup across browsers. We reserve feature switches for specific, high-impact changes that we've found through testing to affect many websites.

We won't create feature switches for every change in behavior and sites cannot opt-in to them. Instead, developers should opt-in to the IE7 mode or IE8 mode through the "X-UA-Compatible" meta tag or header to make their sites compatible until they can update them to IE9 mode.

Other CV List Capabilities: In addition to providing feature switches and the ability to turn off Conditional Comments, the Internet Explorer 9 CV List can also:

  • Display sites in Compatibility View, just like the Internet Explorer 8 CV List did
  • Change the Document Mode in which a site renders to IE7 mode or IE8 mode

Guidance and Tool Usage

The Internet Explorer 9 CV List is an XML file on "". We can update the list daily, which means we can quickly accommodate site developer requests to remove updated sites. Users automatically get updates.

You can view the Internet Explorer 9 CV List on your local machine by navigating to this file path:

File:\\%LOCALAPPDATA%\Microsoft\Internet Explorer\IECompatData\iecompatdata.xml

In order to continue to reduce the size of the CV List, we encourage site developers to update their sites now to work well in Internet Explorer 9 Standards mode and serve the same markup they use with other browsers. At a minimum, sites should take advantage of the Windows Internet Explorer 7 or Internet Explorer 8 document mode by declaring an X-UA-Compatible value until they can update.


  • Verify that your site works well in Internet Explorer 9
  • Use the improved F12 developer tools to resolve any compatibility issues
  • Check the current Internet Explorer 9 CV List located at to see if your site is on the list
  • If it is on the list, clear the Include updated website lists from Microsoft" check box in the Compatibility View Settings dialog box (Alt –> Tools –> Compatibility View Settings).
Compatibility View Settings dialog box with correct check boxes selected

  • Lastly, email with the following information and ask that your site be removed from the Internet Explorer 9 CV List when your updates are live on the web:
  • Owner Name
  • Corporate Title
  • Email Address
  • Telephone Number
  • Company Name
  • Street Address
  • Website Address
Microsoft will review the provided information and remove your site from the Compatibility View List at the next scheduled list update.