Element with lang attribute has valid language tag

Description

This rule checks that a non-empty lang attribute of an element in the page has a language tag with a known primary language subtag.

Applicability

This rule applies to any HTML element with a lang attribute value that is not empty ("") and for which all of the following is true:

descendant: the element is an inclusive descendant in the flat tree of a body element; and
content type: the element has an associated node document with a content type of text/html; and
text: there is some text inheriting its programmatic language from the element which is neither empty nor only whitespace.

Expectation

For each test target, the lang attribute value has a known primary language tag.

Assumptions

This rule assumes that the lang attribute value is used to indicate the language of a section of the content. If the lang attribute value is used for something else (for example to indicate the programming language of a code element), the content may still conform to WCAG despite failing this rule.
This rule assumes that user agents and assistive technologies can programmatically determine known primary language tags even if these do not conform to the RFC 5646 syntax.
This rule assumes that only known primary language tags are enough to satisfy Success Criterion 3.1.2 Language of Parts; this notably excludes grandfathered tags and ISO 639.2 three-letters codes, both having poor support in assistive technologies.
This rule assumes that the text nodes contain text that express something in human language and therefore need a correct programmatic language.

Accessibility Support

There are differences in how assistive technologies handle unknown and invalid language tags. Some will default to the language of the page, whereas others will default to the closest ancestor with a valid lang attribute.

Background

Bibliography

Accessibility Requirements Mapping

3.1.2 Language of Parts (Level AA)
- Learn more about 3.1.2 Language of Parts
- Required for conformance to WCAG 2.0 and later on level AA and higher.
- Outcome mapping:
  - Any failed outcomes: success criterion is not satisfied
  - All passed outcomes: success criterion needs further testing
  - An inapplicable outcome: success criterion needs further testing
H58: Using language attributes to identify changes in the human language
- Learn more about technique H58
- Not required for conformance to any W3C accessibility recommendation.
- Outcome mapping:
  - Any failed outcomes: technique is not satisfied
  - All passed outcomes: technique needs further testing
  - An inapplicable outcome: technique needs further testing

Input Aspects

The following aspects are required in using this rule.

Test Cases

Passed

Passed Example 1

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This article element has a lang attribute value which has a known primary language tag.

<html lang="es">
	<body>
		<article lang="en">
			They wandered into a strange Tiki bar on the edge of the small beach town.
		</article>
	</body>
</html>

Passed Example 2

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This blockquote element has a lang attribute value which has a known primary language tag. The region section (“CH”) in the value is ignored by the rule (and the definition of known primary language tag).

<html lang="en">
	<body>
		<blockquote lang="fr-CH">
			Ils ont trouvé un étrange bar Tiki aux abords de la petite ville balnéaire.
		</blockquote>
	</body>
</html>

Passed Example 3

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This p element has a lang attribute value which has a known primary language tag, but a syntactically invalid region subtag which is ignored by the rule.

<html lang="fr">
	<body>
		<p lang="en-US-GB">
			They wandered into a strange Tiki bar on the edge of the small beach town.
		</p>
	</body>
</html>

Passed Example 4

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This div element has a valid lang attribute value. There is no text inheriting its programmatic language from the article element, therefore its lang attribute is not considered by the rule.

<html lang="fr">
	<body>
		<article lang="invalid">
			<div lang="en">
				They wandered into a strange Tiki bar on the edge of the small beach town.
			</div>
		</article>
	</body>
</html>

Passed Example 5

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This div element has a valid lang attribute value. The accessible name of the image is text inheriting its programmatic language from the div element.

<html lang="es">
	<body>
		<div lang="EN">
			<img src="/test-assets/shared/fireworks.jpg" alt="Fireworks over Paris" />
		</div>
	</body>
</html>

Failed

Failed Example 1

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This article element has a lang attribute value which does not have a known primary language tag because its primary language subtag does not exist in the language subtag registry.

<html lang="es">
	<body>
		<article lang="dutch">
			Zij liepen een vreemde Tiki bar binnen, aan de rand van een dorpje aan het strand.
		</article>
	</body>
</html>

Failed Example 2

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This article element has a lang attribute value which has no known primary language tag.

<html lang="en">
	<body>
		<article lang="#!">
			They wandered into a strange Tiki bar on the edge of the small beach town.
		</article>
	</body>
</html>

Failed Example 3

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This article element has a lang attribute value which consists of only whitespace and thus has no known primary language tag.

<html lang="fr">
	<body>
		<article lang="  ">
			They wandered into a strange Tiki bar on the edge of the small beach town.
		</article>
	</body>
</html>

Failed Example 4

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The lang attribute value does not have a valid language tag. Even though the p element is not included in the accessibility tree due to the presence of the aria-hidden="true" attribute, it is visible; therefore its content is text inheriting its programmatic language from the article element. Hence, the lang attribute must be valid.

<html lang="es">
	<body>
		<article lang="english">
			<p aria-hidden="true">
				They wandered into a strange Tiki bar on the edge of the small beach town.
			</p>
		</article>
	</body>
</html>

Failed Example 5

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The lang attribute value does not have a valid language tag. Even though the p element is not visible due to it being moved off-screen, it is included in the accessibility tree; therefore its content is text inheriting its programmatic language from the article element. Hence, the lang attribute must be valid.

<html lang="fr">
	<body>
		<article lang="English">
			<p style="position: absolute; top: -9999px">
				They wandered into a strange Tiki bar on the edge of the small beach town.
			</p>
		</article>
	</body>
</html>

Failed Example 6

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This div element has an invalid lang attribute value. There is no text inheriting its programmatic language from the article element, therefore its lang attribute is not considered by the rule.

<html lang="es">
	<body>
		<article lang="en">
			<div lang="invalid">
				They wandered into a strange Tiki bar on the edge of the small beach town.
			</div>
		</article>
	</body>
</html>

Failed Example 7

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This div element has an invalid lang attribute value. The accessible name of the image is text inheriting its programmatic language from the div element.

<html lang="en">
	<body>
		<div lang="invalid">
			<img src="/test-assets/shared/fireworks.jpg" alt="Fireworks over Paris" />
		</div>
	</body>
</html>

Failed Example 8

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The lang attribute value of this p element is an iso 639.2 three letters code, which has no known primary language tag.

<html lang="en">
	<body>
		<p lang="eng">I love ACT rules!</p>
	</body>
</html>

Failed Example 9

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The lang attribute value of this p element is a grandfathered tag, which has no known primary language tag.

<html lang="lb">
	<body>
		<p lang="i-lux">Lëtzebuerg ass e Land an Europa.</p>
	</body>
</html>

Inapplicable

Inapplicable Example 1

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There is no element with a lang attribute value which is a descendant of a body element.

<html lang="en">
	<body>
		They wandered into a strange Tiki bar on the edge of the small beach town.
	</body>
</html>

Inapplicable Example 2

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There is no element which is a descendant of a body element and has a non-empty lang attribute value.

<html lang="en">
	<body>
		<article lang="">
			They wandered into a strange Tiki bar on the edge of the small beach town.
		</article>
	</body>
</html>

Inapplicable Example 3

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There is no element with a text node as a descendant in the flat tree that is either visible or included in the accessibility tree.

<html lang="en">
	<body>
		<p lang="hidden">
			<span style="display: none;">
				They wandered into a strange Tiki bar on the edge of the small beach town.
			</span>
		</p>
	</body>
</html>

Inapplicable Example 4

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There is no text inheriting its programmatic language from this div element.

<html lang="en">
	<body>
		<div lang="invalid">
			<img src="/test-assets/shared/fireworks.jpg" alt="" />
		</div>
	</body>
</html>

Inapplicable Example 5

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The text inheriting its programmatic language from this div element is only whitespace.

<html lang="en">
	<body>
		<div lang="invalid"></div>
	</body>
</html>

Glossary

Accessible Name

The accessible name is the programmatically determined name of a user interface element that is included in the accessibility tree.

The accessible name is calculated using the accessible name and description computation.

For native markup languages, such as HTML and SVG, additional information on how to calculate the accessible name can be found in HTML Accessibility API Mappings 1.0, Accessible Name and Description Computation (working draft) and SVG Accessibility API Mappings, Name and Description (working draft).

For more details, see examples of accessible name.

Note: As per the accessible name and description computation, each element always has an accessible name. When no accessible name is provided, the element will nonetheless be assigned an empty ("") one.

Note: As per the accessible name and description computation, accessible names are flat string trimmed of leading and trailing whitespace. Notably, it is not possible for a non-empty accessible name to be composed only of whitespace since these must be trimmed.

Attribute value

The attribute value of a content attribute set on an HTML element is the value that the attribute gets after being parsed and computed according to specifications. It may differ from the value that is actually written in the HTML code due to trimming whitespace or non-digits characters, default values, or case-insensitivity.

Some notable case of attribute value, among others:

For enumerated attributes, the attribute value is either the state of the attribute, or the keyword that maps to it; even for the default states. Thus <input type="image" /> has an attribute value of either Image Button (the state) or image (the keyword mapping to it), both formulations having the same meaning; similarly, “an input element with a type attribute value of Text” can be either <input type="text" />, <input /> (missing value default), or <input type="invalid" /> (invalid value default).
For boolean attributes, the attribute value is true when the attribute is present and false otherwise. Thus <button disabled>, <button disabled="disabled"> and <button disabled=""> all have a disabled attribute value of true.
For attributes whose value is used in a case-insensitive context, the attribute value is the lowercase version of the value written in the HTML code.
For attributes that accept numbers, the attribute value is the result of parsing the value written in the HTML code according to the rules for parsing this kind of number.
For attributes that accept sets of tokens, whether space separated or comma separated, the attribute value is the set of tokens obtained after parsing the set and, depending on the case, converting its items to lowercase (if the set is used in a case-insensitive context).
For aria-* attributes, the attribute value is computed as indicated in the WAI-ARIA specification and the HTML Accessibility API Mappings.

This list is not exhaustive, and only serves as an illustration for some of the most common cases.

The attribute value of an IDL attribute is the value returned on getting it. Note that when an IDL attribute reflects a content attribute, they have the same attribute value.

Focusable

An element is focusable if one or both of the following are true:

the element is part of sequential focus navigation; or
the element has a tabindex value that is not null.

Exception: Elements that lose focus during a period of up to 1 second after gaining focus, without the user interacting with the page the element is on, are not considered focusable.

Notes:

The 1 second time span is an arbitrary limit which is not included in WCAG. Given that scripts can manage the focus state of elements, testing the focusability of an element consistently would be impractical without a time limit.
The tabindex value of an element is the value of the tabindex attribute parsed using the rules for parsing integers. For the tabindex value to be different from null, it needs to be parsed without errors.

Included in the accessibility tree

Elements included in the accessibility tree of platform specific accessibility APIs are exposed to assistive technologies. This allows users of assistive technology to access the elements in a way that meets the requirements of the individual user.

The general rules for when elements are included in the accessibility tree are defined in the core accessibility API mappings. For native markup languages, such as HTML and SVG, additional rules for when elements are included in the accessibility tree can be found in the HTML accessibility API mappings (working draft) and the SVG accessibility API mappings (working draft).

For more details, see examples of included in the accessibility tree.

Programmatically hidden elements are removed from the accessibility tree. However, some browsers will leave focusable elements with an aria-hidden attribute set to true in the accessibility tree. Because they are hidden, these elements are considered not included in the accessibility tree. This may cause confusion for users of assistive technologies because they may still be able to interact with these focusable elements using sequential keyboard navigation, even though the element should not be included in the accessibility tree.

Known Primary Language Tag

A language tag has a known primary language tag if its primary language subtag exists in the language subtag registry with a Type field whose field-body value is language.

A “language tag” is here to be understood as in the first paragraph of the RFC 5646 language tag syntax, i.e. a sequence of subtags separated by hyphens, where a subtag is any sequence of alphanumerical characters. Language tag that are not valid according to the stricter RFC 5646 syntax (and ABNF grammar) definition can still have a known primary language tag. User agents and assistive technologies are more lenient in what they accept. This definition is consistent with the behavior of the :lang() pseudo-selector as defined by Selectors Level 3.

As an example, de-hello would be an accepted way to indicate German in current user agents and assistive technologies, despite not being valid according to RFC 5646 grammar. It has a known primary language tag (namely, de).

As a consequence of this definition, however, grandfathered tags do not have a known primary language tag.

Subtags, notably the primary language subtag, are case insensitive. Comparison with the language subtag registry must be done in a case insensitive way.

Namespaced Element

An element with a specific namespaceURI value from HTML namespaces. For example an “SVG element” is any element with the “SVG namespace”, which is http://www.w3.org/2000/svg.

Namespaced elements are not limited to elements described in a specification. They also include custom elements. Elements such as a and title have a different namespace depending on where they are used. For example a title in an HTML page usually has the HTML namespace. When used in an svg element, a title element has the SVG namespace instead.

Outcome

An outcome is a conclusion that comes from evaluating an ACT Rule on a test subject or one of its constituent test target. An outcome can be one of the three following types:

Inapplicable: No part of the test subject matches the applicability
Passed: A test target meets all expectations
Failed: A test target does not meet all expectations

Note: A rule has one passed or failed outcome for every test target. When there are no test targets the rule has one inapplicable outcome. This means that each test subject will have one or more outcomes.

Note: Implementations using the EARL10-Schema can express the outcome with the outcome property. In addition to passed, failed and inapplicable, EARL 1.0 also defined an incomplete outcome. While this cannot be the outcome of an ACT Rule when applied in its entirety, it often happens that rules are only partially evaluated. For example, when applicability was automated, but the expectations have to be evaluated manually. Such “interim” results can be expressed with the incomplete outcome.

Programmatically Hidden

An HTML element is programmatically hidden if either it has a computed CSS property visibility whose value is not visible; or at least one of the following is true for any of its inclusive ancestors in the flat tree:

has a computed CSS property display of none; or
has an aria-hidden attribute set to true

Note: Contrary to the other conditions, the visibility CSS property may be reverted by descendants.

Note: The HTML standard suggests setting the CSS display property to none for elements with the hidden attribute. While not required by HTML, all modern browsers follow this suggestion. Because of this the hidden attribute is not used in this definition. In browsers that use this suggestion, overriding the CSS display property can reveal elements with the hidden attribute.

Text Inheriting its Programmatic Language from an Element

The text inheriting its programmatic language from an element E is composed of all the following texts:

text nodes: the value of any text nodes that are visible or included in the accessibility tree and children of an element inheriting its programmatic language from E;
accessible text: the accessible name and accessible description of any element inheriting its programmatic language from E, and included in the accessibility tree;
page title: the value of the document title, only if E is a document in a top-level browsing context.

An element F is an element inheriting its programmatic language from an element E if at least one of the following conditions is true (recursively):

F is E itself (an element always inherits its programmatic language from itself); or
F does not have a non-empty lang attribute, and is the child in the flat tree of an element inheriting its programmatic language from E; or
F is a fully active document element, has no non-empty lang attribute, and its browsing context container is an element inheriting its programmatic language from E.

Visible

Content perceivable through sight.

Content is considered visible if making it fully transparent would result in a difference in the pixels rendered for any part of the document that is currently within the viewport or can be brought into the viewport via scrolling.

Content is defined in WCAG.

For more details, see examples of visible.

Whitespace

Whitespace are characters that have the Unicode “White_Space” property in the Unicode properties list.

This includes:

all characters in the Unicode Separator categories, and
the following characters in the Other, Control category:
- Character tabulation (U+0009)
- Line Feed (LF) (U+000A)
- Line Tabulation (U+000B)
- Form Feed (FF) (U+000C)
- Carriage Return (CR) (U+000D)
- Next Line (NEL) (U+0085)

Rule Versions

Latest version, 20 December 2023 (compare)
- Update example descriptions of failed example 4 and 5
Previous version, 23 June 2022 (compare)
- Account for whitespace in the applicability
- Add assumption about text containing human language
- Account for focus redirects in "focusable" definition
Previous version, 28 January 2022

Implementations

This section is not part of the official rule. It is populated dynamically and not accounted for in the change history or the last modified date.

Implementation	Type	Consistency
Alfa (fully automated) 0.80.0	Automated tool	Consistent
Alfa (semi-automated) 0.80.0	Semi-automated tool	Consistent
Axe DevTools Pro 4.37.1	Semi-automated tool	Consistent
Axe-core 4.8.3	Automated tool	Consistent
Equal Access Accessibility Checker 3.1.42-rc.0	Automated tool	Consistent
QualWeb 3.0.0	Automated tool	Consistent
SortSite 6.45	Automated tool	Consistent
Total Validator 17.4.0	Linter	Consistent
Total Validator (+Browser) 17.4.0	Automated tool	Consistent