HTML Guide

This document appears to be written in X. Consider adding “lang="y"” (or variant) to the “html” start tag.

lang

This validation issue indicates that your HTML document does not specify a language for its content. Specifying the document’s language is important for accessibility, search engines, and browser behavior.

To fix this, you need to add the lang attribute to the <html> element, indicating the primary language of the document. For example, if your document is written in Spanish, you should set the lang attribute to "es".

Here’s how to do it:

Original HTML (without `lang` attribute)

<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <title>Mi Sitio Web</title>
</head>
<body>
    <h1>Bienvenido a mi sitio web</h1>
    <p>Este es un párrafo en español.</p>
</body>
</html>

Updated HTML (with `lang` attribute)

<!DOCTYPE html>
<html lang="es">
<head>
    <meta charset="UTF-8">
    <title>Mi Sitio Web</title>
</head>
<body>
    <h1>Bienvenido a mi sitio web</h1>
    <p>Este es un párrafo en español.</p>
</body>
</html>

Explanation

The lang="es" attribute specifies that the primary language of the document is Spanish.
Setting the lang attribute helps screen readers and other assistive technologies to better interpret the content.
It also provides crucial information for search engines and browsers, improving the accessibility and search engine optimization (SEO) of your website.

If you need to specify a regional variation of Spanish, you can use values like lang="es-ES" for Spanish as used in Spain, or lang="es-MX" for Spanish as used in Mexico.

Example with Regional Variation

<!DOCTYPE html>
<html lang="es-MX">
<head>
    <meta charset="UTF-8">
    <title>Mi Sitio Web</title>
</head>
<body>
    <h1>Bienvenido a mi sitio web</h1>
    <p>Este es un párrafo en español de México.</p>
</body>
</html>

By adding the lang attribute with the appropriate value, you’ll resolve the W3C HTML Validator issue.

Learn more:

MDN: the lang attribute

Related W3C validator issues

Attribute “isolang” not allowed on element “html” at this point.

Instead of using the isolang attribute to define the language of the document, you can use lang with an ISO 639-1 two character code.

For example, for Portuguese:

<html lang="pt">

Bad value X for attribute “lang” on element “html”: The language subtag X is not a valid ISO language part of a language tag.

Consider adding a “lang” attribute to the “html” start tag to declare the language of this document.

lang

This document appears to be written in Arabic. Consider adding “dir="rtl"” to the “html” start tag.

Based on the content of the document, the W3C Validator has determined that it’s written in Arabic, and it suggests you specify the direction of text from right to left like this:

<html dir="rtl" lang="ar">

This document appears to be written in English but the “html” start tag has an empty “lang” attribute. Consider using “lang="en"” (or variant) instead.

lang

Based on the content of the document, the W3C validator thinks that it’s written in English. Consider explicitly specifying the language using the lang property.

Example:

<html lang="en">

This document appears to be written in English but the “html” start tag has X

lang

Based on the content of the document, the W3C validator thinks that it’s written in English, but the lang property in the <html> element specifies a different language. Check the language of the document, if it matches the lang property you can safely ignore and mute this warning.

Example:

<html lang="fr">

This document appears to be written in X but the “html” start tag has “lang=Y”.

lang

When the attribute “xml:lang” in no namespace is specified, the element must also have the attribute “lang” present with the same value.