# HTML elements with lang and xml:lang must have the same base language
> Canonical HTML version: https://rocketvalidator.com/accessibility-validation/axe/4.11/html-xml-lang-mismatch
> Attribution: Rocket Validator (https://rocketvalidator.com)
> License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/)
The `lang` attribute tells browsers and assistive technologies what language the content is written in. The `xml:lang` attribute serves the same purpose but comes from the XML/XHTML specification. When both attributes are present on the same element—most commonly the `` element—they must agree on the base language. The "base language" is the primary language subtag (e.g., `en` in `en-US` or `fr` in `fr-CA`). If one attribute says `en` and the other says `fr`, assistive technologies receive conflicting information and cannot reliably determine how to process the content.
## Who is affected
This issue primarily impacts **screen reader users**, including people who are blind, deafblind, or have cognitive disabilities. Screen readers maintain separate pronunciation libraries for each language. When they encounter a language declaration, they switch to the appropriate library so words are spoken with correct pronunciation and cadence. A mismatch between `lang` and `xml:lang` can cause the screen reader to select the wrong library or behave unpredictably, making the content difficult or impossible to understand.
Users who speak multiple languages and browse sites in different languages are especially vulnerable, as they rely on accurate language declarations to switch between language contexts.
## Related WCAG success criteria
This rule relates to **WCAG Success Criterion 3.1.1: Language of Page** (Level A), which requires that the default human language of each web page can be programmatically determined. This criterion applies across WCAG 2.0, 2.1, and 2.2, as well as EN 301 549 and RGAA. When `lang` and `xml:lang` conflict, the programmatically determined language becomes ambiguous, violating this requirement.
## How to fix it
1. **Check the `` element** (and any other elements) for the presence of both `lang` and `xml:lang` attributes.
2. **Ensure both attributes use the same base language.** For example, if `lang="en"`, then `xml:lang` must also start with `en` (e.g., `en`, `en-US`, or `en-GB`).
3. **If you don't need `xml:lang`**, the simplest fix is to remove it entirely. The `lang` attribute alone is sufficient for HTML5 documents.
4. **If you're serving XHTML**, both attributes may be required. In that case, keep them in sync.
You can find valid language codes on the [ISO 639 language codes](https://www.loc.gov/standards/iso639-2/php/code_list.php) reference page. Common codes include `en` for English, `fr` for French, `es` for Spanish, `de` for German, and `ar` for Arabic.
## Examples
### Incorrect: mismatched base languages
The `lang` attribute specifies English, but `xml:lang` specifies French. This creates a conflict that confuses assistive technologies.
```html
My Page
Hello, world!
```
### Correct: matching base languages
Both attributes specify English. The dialect subtag may differ, but the base language (`en`) is the same.
```html
My Page
Hello, world!
```
### Correct: identical values
The simplest and most reliable approach—use the exact same value for both attributes.
```html
My Page
Hello, world!
```
### Correct: only `lang` attribute (HTML5)
In HTML5 documents, the `xml:lang` attribute is not required. Using `lang` alone avoids any possibility of a mismatch.
```html
My Page
Hello, world!
```
### Correct: specifying language on inline elements
When content in a different language appears within the page, use the `lang` attribute on the appropriate element. If you also use `xml:lang`, make sure they match.
```html
Welcome to our site. Bienvenidos a nuestro sitio.
```
For right-to-left languages, also include the `dir` attribute:
```html
مرحبا بكم في موقعنا
```