HTML page has lang attribute

Applicability

This rule applies to any document element if it is an html element for which all the following are true:

is in a top-level browsing context; and
has a node document with a content type of text/html.

Note: html elements within iframe and object elements are not applicable as iframe and object elements create nested browsing contexts. However, as these elements are meant to provide a layer of isolation, the declared language of their parent browsing context will likely not be inherited, making it possible for empty lang attributes in nested browsing contexts to also cause accessibility issues.

Expectation

Each test target has a lang [attribute value][] that is neither empty ("") nor only ASCII whitespace.

Assumptions

The language of the page can be set by other methods than the lang attribute, for example using HTTP headers or the meta element. These methods are not supported by all assistive technologies. This rule assumes that these other methods are insufficient to satisfying Success Criterion 3.1.1: Language of Page.

Accessibility Support

There are no accessibility support issues known.

Background

Related rules

Bibliography

Test Cases

Passed

Passed Example 1

This html element has a lang attribute with a non-empty ("") value.

<html lang="en">
	<body>
		The quick brown fox jumps over the lazy dog.
	</body>
</html>

Failed

Failed Example 1

This html element does not have a lang attribute.

<html>
	<body>
		The quick brown fox jumps over the lazy dog.
	</body>
</html>

Failed Example 2

This html element has a lang attribute with an empty ("") value.

<html lang="">
	<body>
		The quick brown fox jumps over the lazy dog.
	</body>
</html>

Failed Example 3

This html element has a lang attribute whose value is only ASCII whitespace.

<html lang=" ">
	<body>
		The quick brown fox jumps over the lazy dog.
	</body>
</html>

Failed Example 4

This html element has no lang attribute, only a xml:lang attribute.

<html xml:lang="en">
	<body>
		The quick brown fox jumps over the lazy dog.
	</body>
</html>

Inapplicable

Inapplicable Example 1

This rule does not apply to an svg element.

<svg xmlns="http://www.w3.org/2000/svg" lang="en">
    <text>
        The quick brown fox jumps over the lazy dog.
    </text>
</svg>

Inapplicable Example 2

This rule does not apply to a math element.

<math lang="en">
    The quick brown fox jumps over the lazy dog.
</math>

AI Prompt

Create a PHP class in the namespace "App\Services\AccessibilityAnalyzer\ActRules"
that extends "App\Services\AccessibilityAnalyzer\ActRuleRunner" and is called "HtmlPageLangB5c3f8" that has a function with the signature "protected function findApplicableElements(Crawler $crawler): Crawler". The base class includes the function "protected function isElementIncludedInAccessibilityTree(\DOMNode $element): bool" for determining if an element is included in the accessibility tree.

Web accessibility rule:

# HTML page has lang attribute

metadata:
    id: b5c3f8
    name: 'HTML page has lang attribute'
    rule_type: atomic
    description: "This rule checks that an HTML page has a non-empty `lang` attribute.\n"
    accessibility_requirements: { 'wcag20:3.1.1': { forConformance: true, failed: 'not satisfied', passed: 'further testing needed', inapplicable: 'further testing needed' }, 'wcag-technique:H57': { forConformance: false, failed: 'not satisfied', passed: 'further testing needed', inapplicable: 'further testing needed' } }
    input_aspects: ['DOM Tree']
    acknowledgments: { authors: ['Jey Nandakumar'], previous_authors: ['Annika Nietzio'], funding: [WAI-Tools] }

## Applicability

This rule applies to any [document element](https://dom.spec.whatwg.org/#document-element) if it is an `html` element for which all the following are true:

- is in a [top-level browsing context](https://html.spec.whatwg.org/#top-level-browsing-context); and
- has a [node document](https://dom.spec.whatwg.org/#concept-node-document) with a [content type](https://dom.spec.whatwg.org/#concept-document-content-type) of `text/html`.

**Note:** `html` elements within `iframe` and `object` elements are not applicable as `iframe` and `object` elements create [nested browsing contexts](https://html.spec.whatwg.org/#nested-browsing-context). However, as these elements are meant to provide a layer of isolation, the declared language of their [parent browsing context](https://html.spec.whatwg.org/#parent-browsing-context) will likely not be inherited, making it possible for empty `lang` attributes in [nested browsing contexts](https://html.spec.whatwg.org/#nested-browsing-context) to also cause accessibility issues.

## Expectation

Each test target has a `lang` [attribute value][] that is neither empty (`""`) nor only [ASCII whitespace](https://infra.spec.whatwg.org/#ascii-whitespace).

## Assumptions

The language of the page can be set by other methods than the `lang` attribute, for example using HTTP headers or the `meta` element. These methods are not supported by all assistive technologies. This rule assumes that these other methods are insufficient to satisfying [Success Criterion 3.1.1: Language of Page](https://www.w3.org/TR/WCAG22/#language-of-page).

## Accessibility Support

There are no accessibility support issues known.

## Background

### Related rules

- [HTML page `lang` attribute has valid language tag](https://www.w3.org/WAI/standards-guidelines/act/rules/bf051a/)
- [HTML page language subtag matches default language](https://www.w3.org/WAI/standards-guidelines/act/rules/ucwvc8/)

### Bibliography

- [Understanding Success Criterion 3.1.1: Language of Page](https://www.w3.org/WAI/WCAG22/Understanding/language-of-page.html)
- [H57: Using language attributes on the html element](https://www.w3.org/WAI/WCAG22/Techniques/html/H57)
- [RFC 5646: Tags for Identifying Languages](https://www.rfc-editor.org/rfc/rfc5646.html)
- [The `lang` and `xml:lang` attributes](https://html.spec.whatwg.org/multipage/dom.html#the-lang-and-xml:lang-attributes)

## Test Cases

### Passed

#### Passed Example 1

This `html` element has a `lang` attribute with a non-empty (`""`) value.

```html
<html lang="en">
	<body>
		The quick brown fox jumps over the lazy dog.
	</body>
</html>
```

### Failed

#### Failed Example 1

This `html` element does not have a `lang` attribute.

```html
<html>
	<body>
		The quick brown fox jumps over the lazy dog.
	</body>
</html>
```

#### Failed Example 2

This `html` element has a `lang` attribute with an empty (`""`) value.

```html
<html lang="">
	<body>
		The quick brown fox jumps over the lazy dog.
	</body>
</html>
```

#### Failed Example 3

This `html` element has a `lang` attribute whose value is only [ASCII whitespace](https://infra.spec.whatwg.org/#ascii-whitespace).

```html
<html lang=" ">
	<body>
		The quick brown fox jumps over the lazy dog.
	</body>
</html>
```

#### Failed Example 4

This `html` element has no `lang` attribute, only a `xml:lang` attribute.

```html
<html xml:lang="en">
	<body>
		The quick brown fox jumps over the lazy dog.
	</body>
</html>
```

### Inapplicable

#### Inapplicable Example 1

This rule does not apply to an `svg` element.

```svg
<svg xmlns="http://www.w3.org/2000/svg" lang="en">
    <text>
        The quick brown fox jumps over the lazy dog.
    </text>
</svg>
```

#### Inapplicable Example 2

This rule does not apply to a `math` element.

```xml
<math lang="en">
    The quick brown fox jumps over the lazy dog.
</math>
```