HTML Guides for X-UA-Compatible
Learn how to identify and fix common HTML validation errors flagged by the W3C Validator — so your pages are standards-compliant and render correctly across every browser. Also check our Accessibility Guides.
The X-UA-Compatible meta tag was originally introduced to control which rendering engine Internet Explorer would use to display a page. Developers could force IE to emulate older versions (e.g., IE=7, IE=9) or use the latest available engine with IE=edge. The value IE=edge,chrome=1 was also commonly used to activate the Google Chrome Frame plugin, which allowed Internet Explorer to use Chrome’s rendering engine instead.
The HTML specification now only permits the value IE=edge for this meta tag. Other values are considered invalid for several reasons:
- Google Chrome Frame is discontinued. The chrome=1 directive targeted a plugin that was retired in February 2014 and is no longer supported by any browser.
- Legacy IE rendering modes are obsolete. Internet Explorer itself has been retired, making emulation modes like IE=EmulateIE7 or IE=9 pointless.
- Standards compliance. The WHATWG HTML living standard explicitly requires the content attribute value to be IE=edge when http-equiv="X-UA-Compatible" is used.
In practice, since all modern browsers use their latest rendering engine by default, this meta tag has little functional impact today. If your site no longer needs to support Internet Explorer at all, you can safely remove the tag entirely. If you choose to keep it — for example, in environments where legacy IE browsers might still access your site — ensure the value is exactly IE=edge.
Examples
Invalid: Using chrome=1 with IE=edge
This was a common pattern when Google Chrome Frame was active, but it now triggers a validation error:
<meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1">Invalid: Using a legacy IE rendering mode
Forcing a specific IE version is no longer valid:
<meta http-equiv="X-UA-Compatible" content="IE=EmulateIE7">Invalid: Specifying a particular IE version
<meta http-equiv="X-UA-Compatible" content="IE=9">Valid: Using IE=edge
The only accepted value is IE=edge:
<meta http-equiv="X-UA-Compatible" content="IE=edge">Valid: Removing the tag entirely
If you don’t need Internet Explorer compatibility, the simplest fix is to remove the meta tag altogether. A minimal valid document without it:
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>My Page</title>
</head>
<body>
<p>Hello, world!</p>
</body>
</html>The X-UA-Compatible meta tag or HTTP header value must be set to IE=edge instead of IE=10 for modern browser compatibility.
The X-UA-Compatible HTTP header or <meta http-equiv="X-UA-Compatible"> element instructs Internet Explorer which document mode to use. Setting it to IE=10 forces the page into IE10 rendering mode, which is outdated and may cause issues with modern web standards. The recommended value is IE=edge, which tells IE to use the highest supported mode available, ensuring the browser uses the latest standards.
Example of the correct <meta> tag for compliance:
<!DOCTYPE html>
<html lang="en">
<head>
<title>Correct X-UA-Compatible Example</title>
<meta http-equiv="X-UA-Compatible" content="IE=edge">
</head>
<body>
<!-- Page content -->
</body>
</html>Remove any instance like IE=10 and replace with IE=edge to resolve the validator issue.
The X-UA-Compatible header tells Internet Explorer which rendering engine to use for a page. Setting it to IE=edge instructs IE to use the highest available standards mode, ensuring the best compatibility and avoiding legacy rendering quirks. The ,chrome=1 directive was an addition that told browsers with the Google Chrome Frame plugin installed to use Chrome’s rendering engine instead of IE’s. Google discontinued Chrome Frame in 2014, and the W3C validator only accepts IE=edge as a valid value for this header.
Including the deprecated chrome=1 directive causes a validation error and serves no practical purpose on modern websites. No current browser recognizes or acts on it, so it’s dead code that only creates noise in your markup.
The fix is straightforward: remove ,chrome=1 from the content attribute, leaving only IE=edge.
Examples
Incorrect
The following triggers the validation error because of the ,chrome=1 suffix:
<meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1">Correct
Simply use IE=edge as the sole value:
<meta http-equiv="X-UA-Compatible" content="IE=edge">Full document example
If you include this meta tag in a complete HTML document, place it early in the <head>:
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<title>My Web Page</title>
</head>
<body>
<h1>Hello World</h1>
</body>
</html>Server-side configuration
If you set X-UA-Compatible as an HTTP response header rather than a meta tag, apply the same fix there. For example, in an Apache .htaccess file:
<IfModule mod_headers.c>
Header set X-UA-Compatible "IE=edge"
</IfModule>In Nginx:
add_header X-UA-Compatible "IE=edge";Is this meta tag still needed?
With Internet Explorer reaching end of life, the X-UA-Compatible meta tag itself is largely unnecessary for new projects. If your site no longer needs to support IE, you can safely remove the tag entirely. If you do keep it for legacy support, ensure the value is exactly IE=edge with no additional directives.
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