22.214.171.124 How Internet Explorer Chooses Between Document Modes
By default, Windows Internet Explorer 8 uses IE8 mode, Windows
Internet Explorer 9 uses IE9 mode, etc. However, Windows Internet Explorer uses
several criteria to determine which document mode to use. For example, if an
HTML page contains a valid
declaration (see [HTML5:2014]),
Internet Explorer uses one of the standards-based document modes. But, if there
is no valid
, Internet Explorer uses Quirks Mode. Microsoft Edge is
designed to be interoperable for the web and is designed primarily to run in
EdgeHTML mode. Only when there is no
declaration does a page render in Quirks Mode.
The following rules determine how Internet Explorer selects the document mode:
1. The Developer Tools setting overrides any document mode specified by a webpage. The setting remains active for the lifetime of the tab.
2. In Internet Explorer 9, if the document is hosted in an iframe element, the document mode is determined by the document mode of the top-level webpage. Subdocuments cannot be rendered in IE9 mode unless the top-level document is also in IE9 mode.
3. A meta tag
with a value of
a HTTP response header can override items in the Compatibility View Settings
list and the doctype unless the X-UA-Compatible value is a Compatibility
View setting, such as
4. The Compatibility View settings can force a webpage to be displayed in a less-standard document mode.
5. The Local Compatibility Site list, the Microsoft Compatibility Site list and the Enterprise Mode IE Compatibility Site list can force a webpage to be displayed in other document modes.
6. Group Policy settings override settings and force all webpages to be displayed in the specified document mode.
7. If none of these
rules apply, the
determines whether the webpage renders in a standards mode, Almost Standards
mode, or Quirks Mode.
The following rules determine how Microsoft Edge selects the document mode:
The <!DOCTYPE> declaration determines whether the webpage renders some specific Quirks Mode emulation (QME) behaviors called out in the [MS-HTML5] and [MS-CSS21] documentation.
The following sections explain how these rules affect how Internet Explorer selects between document modes. Most of these sections do not apply to Microsoft Edge unless explicitly called out.