# This document appears to be written in X. Consider adding “lang="y"” (or variant) to the “html” start tag.
> Canonical HTML version: https://rocketvalidator.com/html-validation/this-document-appears-to-be-written-in-x-consider-adding-lang-y-or-variant-to-the-html-start-tag
> Attribution: Rocket Validator (https://rocketvalidator.com)
> License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/)
The `lang` attribute on the `` element declares the primary language of the document's content. When this attribute is missing or set incorrectly, the validator analyzes the text content and attempts to detect the language automatically. If it identifies a likely language, it produces this warning suggesting you add the appropriate `lang` value.
This matters for several important reasons:
- **Accessibility:** Screen readers rely on the `lang` attribute to select the correct pronunciation rules and voice profile. Without it, a screen reader might attempt to read Spanish text using English phonetics, producing unintelligible speech for the user.
- **Browser behavior:** Browsers use the language declaration for hyphenation, quotation mark styling, spell-checking, and font selection. For example, the CSS `hyphens: auto` property depends on the `lang` attribute to apply language-appropriate hyphenation rules.
- **Search engines:** Search engines use the `lang` attribute as a signal to understand the language of your content, which helps serve it to the right audience in search results.
- **Translation tools:** Automatic translation services use the declared language to determine whether (and from which language) to offer translation.
The value of the `lang` attribute must be a valid BCP 47 language tag. Common examples include `en` (English), `es` (Spanish), `fr` (French), `de` (German), `zh` (Chinese), `ja` (Japanese), and `ar` (Arabic). You can also specify regional variants like `en-US`, `en-GB`, `pt-BR`, or `es-MX`.
## Examples
### Missing `lang` attribute
This triggers the warning because the validator detects the content language but finds no `lang` declaration:
```html
Mi Sitio Web
Bienvenido a mi sitio web
Este es un párrafo en español.
```
### Fixed with the correct `lang` attribute
Adding `lang="es"` tells browsers, screen readers, and search engines that this document is in Spanish:
```html
Mi Sitio Web
Bienvenido a mi sitio web
Este es un párrafo en español.
```
### Mismatched `lang` attribute
This can also trigger the warning when the `lang` value doesn't match the actual content. Here, the content is in French but the language is declared as English:
```html
Mon Site Web
Bienvenue sur mon site web
Ceci est un paragraphe en français.
```
The fix is to correct the `lang` value to match the content:
```html
Mon Site Web
Bienvenue sur mon site web
Ceci est un paragraphe en français.
```
### Using a regional variant
If you need to specify a regional variation, append the region subtag. For example, `es-MX` for Mexican Spanish or `pt-BR` for Brazilian Portuguese:
```html
Mi Sitio Web
Bienvenido a mi sitio web
Este es un párrafo en español de México.
```
### Sections in a different language
When your document is primarily in one language but contains sections in another, set the main language on `` and use `lang` on individual elements for the exceptions:
```html
My Website
Welcome to my website
This site is available in multiple languages.
Bienvenido a mi sitio web.
```
This approach ensures that assistive technologies switch pronunciation rules appropriately when they encounter the foreign-language section, while browsers and search engines still understand the primary document language.