IE9 Compatibility Mode Enabler: Quick Guide to Restore Legacy Rendering

IE9 Compatibility Mode Enabler: Step-by-Step Setup for Developers

Summary

A short, reliable way to force Internet Explorer 9 document mode is to use the X-UA-Compatible header or meta tag and, for managed environments, Enterprise/IE Mode site lists. Below are step-by-step instructions, troubleshooting tips, and best practices.

1) Choose header vs. meta tag

• Prefer an HTTP response header when you control the server (more reliable).
  Example header:

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  X-UA-Compatible: IE=9 

• Use a meta tag only if you cannot change server headers. It must appear as the first element inside(immediately after opening) to be effective:

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  <meta http-equiv=“X-UA-Compatible” content=“IE=9” />
  

2) Which value to use

• IE=9 — force standards rendering as IE9.
• IE=EmulateIE9 — use DOCTYPE to decide standards vs quirks, but target IE9 rendering.
• IE=edge — let the browser use its highest available mode (not recommended if you must lock to IE9).

Choose IE=9 when you need consistent IE9 behavior regardless of DOCTYPE.

3) Server configuration examples

• Apache (in .htaccess or server config):

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  Header set X-UA-Compatible “IE=9” 

• Nginx: “` add_header X-UA