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HTML Guide

X-UA-Compatible HTTP header must have the value “IE=edge”, was “IE=edge,chrome=1”.

Setting the X-UA-Compatible HTTP header with the value IE=edge,chrome=1 is non-standard; it should be set to IE=edge only.

The X-UA-Compatible header is used to specify how Internet Explorer should render a webpage. It allows web developers to opt into the latest standards mode in IE, thus ensuring better compatibility and performance by avoiding compatibility modes that simulate older browser versions. Setting it to IE=edge tells IE to use the highest mode available, which is the most standards-compliant mode the browser supports. The additional ,chrome=1 directive was used for a Google Chrome Frame feature, which is now deprecated and should not be used in modern webpages.

To ensure your HTML document meets the W3C standards, you must remove ,chrome=1 and just have the IE=edge value. Here’s how you can properly set the X-UA-Compatible header:

  1. In HTML Meta Tags: Ensure your meta tag within the HTML document head is correctly written. 
<!DOCTYPE html>
<html lang="en">
<head>
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <title>My Web Page</title>
</head>
<body>
  <h1>Hello World</h1>
</body>
</html>
  1. In HTTP Headers: If you’re setting the X-UA-Compatible via server configuration, for example in an .htaccess file (for Apache), ensure it’s configured without the ,chrome=1. 
# .htaccess example
<IfModule mod_headers.c>
  Header set X-UA-Compatible "IE=edge"
</IfModule>

Correctly setting this ensures that your page is rendered with the most up-to-date rendering engine, enhancing compatibility and performance across modern web standards.

Learn more:

Related W3C validator issues

A “meta” element with an “http-equiv” attribute whose value is “X-UA-Compatible” must have a “content” attribute with the value “IE=edge”.