Validación HTML: Bad value “cleartype” for attribute “http-equiv” on element “meta”.

Acerca de este problema HTML

The http-equiv attribute on <meta> elements acts as a pragma directive, simulating the effect of an HTTP response header. The HTML specification defines a strict list of allowed values, including content-type, default-style, refresh, x-ua-compatible, and content-security-policy. Any value not on this list — such as cleartype — is considered invalid and will trigger a validation error.

The <meta http-equiv="cleartype" content="on"> tag was a proprietary Microsoft extension designed to activate ClearType text smoothing in Internet Explorer Mobile 6 and 7 on Windows Phone. ClearType is a sub-pixel rendering technology that improves the readability of text on LCD screens. Since these browsers are long obsolete, this meta tag serves no practical purpose today. No modern browser recognizes or acts on it.

Keeping invalid meta tags in your HTML has several downsides:

Standards compliance: It produces W3C validation errors, which can mask other, more important issues in your markup.
Code cleanliness: Dead code clutters your document head and confuses developers who may not know its history.
No functional benefit: Since no current browser or rendering engine uses this directive, it provides zero value.

The fix is straightforward: remove the <meta http-equiv="cleartype"> tag. If your project requires smooth font rendering on modern browsers, CSS properties like font-smooth (non-standard) or -webkit-font-smoothing and -moz-osx-font-smoothing can be used instead, though these are also non-standard and should be used with care.

Examples

❌ Invalid: Using `cleartype` as an `http-equiv` value

<head>
  <meta charset="utf-8">
  <meta http-equiv="cleartype" content="on">
  <title>My Page</title>
</head>

This triggers the validation error because cleartype is not a valid value for http-equiv.

✅ Fixed: Remove the invalid meta tag

<head>
  <meta charset="utf-8">
  <title>My Page</title>
</head>

Simply removing the tag resolves the error with no loss of functionality in modern browsers.

✅ Alternative: Use CSS for font smoothing if needed

If you want to influence text rendering, use CSS instead of a non-standard meta tag:

body {
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

Note that these CSS properties are themselves non-standard and primarily affect macOS and iOS rendering. On Windows, modern browsers already apply ClearType or DirectWrite smoothing automatically without any developer intervention.