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Forcing a specific IE version is no longer valid: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 directive was introduced to control which rendering engine Internet Explorer would use when displaying a page. Setting it to a specific version like IE=10 locks the page into that version’s rendering mode, even if the user has a newer version of Internet Explorer installed. This is problematic because it prevents the browser from using its most capable, standards-compliant rendering engine and can lead to unexpected layout or functionality issues.
The value IE=edge tells Internet Explorer to use the latest rendering engine available, which ensures the best possible standards compliance and feature support. The HTML specification and the W3C validator enforce this requirement because pinning to a specific IE version serves no forward-compatible purpose and can actively degrade the browsing experience.
It’s worth noting that with Internet Explorer now being retired and replaced by Microsoft Edge, this meta tag is largely historical. However, if you include it at all, the validator requires that it be set to IE=edge. If your site no longer needs to support legacy versions of Internet Explorer, you can also simply remove the X-UA-Compatible declaration entirely — modern browsers ignore it.
How to fix it
- Find any <meta http-equiv="X-UA-Compatible"> tag in your HTML <head>.
- Change the content attribute value from the specific version (e.g., IE=10) to IE=edge.
- If the directive is set as an HTTP response header on your server, update the header value there as well.
- Alternatively, remove the tag or header entirely if you no longer need IE compatibility.
Examples
Incorrect: pinned to a specific IE version
This triggers the validator error because IE=10 locks rendering to Internet Explorer 10 mode:
<meta http-equiv="X-UA-Compatible" content="IE=10">Other version-specific values that would also trigger this error include IE=9, IE=11, IE=EmulateIE10, and similar variations.
Correct: using IE=edge
Replace the version-specific value with IE=edge:
<meta http-equiv="X-UA-Compatible" content="IE=edge">Correct: full document example
When included in a complete HTML document, the X-UA-Compatible meta tag should appear early in the <head>, ideally right after the <meta charset> declaration:
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<title>My Page</title>
</head>
<body>
<p>Page content goes here.</p>
</body>
</html>Correct: removing the tag entirely
If IE support is no longer a concern, the simplest fix is to remove the meta tag altogether:
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>My Page</title>
</head>
<body>
<p>Page content goes here.</p>
</body>
</html>Server-side HTTP header
If the X-UA-Compatible value is being sent as an HTTP response header rather than a meta tag, update your server configuration. For example, in Apache:
# Incorrect
Header set X-UA-Compatible "IE=10"
# Correct
Header set X-UA-Compatible "IE=edge"Or in Nginx:
# Incorrect
add_header X-UA-Compatible "IE=10";
# Correct
add_header X-UA-Compatible "IE=edge";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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