HTML element language subtag matches language

  • Rule Type:atomic
  • Rule Id: off6ek
  • Last modified: Feb 11, 2021
  • 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 is satisfied.
        • 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 to conformance to any W3C accessibility recommendation.
      • Outcome mapping:
        • Any failed outcomes: technique is not satisfied.
        • All passed outcomes: technique is satisfied.
        • An inapplicable outcome: technique is satisfied.

Description

This rule checks that the primary language subtag of an element matches its default language

Applicability

This rule applies to any HTML element with a lang attribute for which all the following are true:

Expectation

For each test target, the primary language of its lang attribute value is a most common language of the test target.

Assumptions

Accessibility Support

There are no major accessibility support issues known for this rule.

Background

This rule checks that, if a lang attribute is used, its value is correct with respect to the content. This rule does not check whether a lang attribute should have been used or not. Especially, this rule does not check when lang attributes are missing. This must be tested separately and it is therefore possible to pass this rule without satisfying Success Criterion 3.1.2 Language of Parts.

In all examples, the html element has itself a lang attribute in order to make sure that the examples satisfy Success Criterion 3.1.1 Language of Page. These html elements are, however, never applicable because they are not descendants of a body element, and the example descriptions do not mention them further.

Test Cases

Passed

Passed Example 1

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This span element has a lang attribute value of nl (Dutch), which matches its most common language. The most common language is Dutch because all words are Dutch.

<html lang="en">
	<head>
		<title>Dutch idioms</title>
	</head>
	<body>
		<p>
			The Dutch phrase <span lang="nl">"Hij ging met de kippen op stok"</span> literally translates into "He went to
			roost with the chickens", but it means that he went to bed early.
		</p>
	</body>
</html>

Passed Example 2

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The second p element has lang attribute value of nl (Dutch), which matches its most common language. The most common language is Dutch because all English words are in span elements with a lang attribute value of en. Both span elements also have a lang attribute matching their most common language.

<html lang="en">
	<head>
		<title>Dutch idioms</title>
	</head>
	<body>
		<p>Dutch idioms and their English meaning.</p>
		<p lang="nl">
			<span lang="en">The Dutch phrase</span> "Hij ging met de kippen op stok"
			<span lang="en"
				>literally translates into "He went to roost with the chickens", but it means that he went to bed early.</span
			>
		</p>
	</body>
</html>

Passed Example 3

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This div element has a lang attribute value of en (English), which matches its most common language. The most common language is English because the accessible texts are English, and all other text is in a p element with a (correct) lang attribute value of fr.

<html lang="fr">
	<head>
		<title>Feu d'artifice du nouvel an</title>
	</head>
	<body>
		<div lang="en">
			<img src="/test-assets/shared/fireworks.jpg" alt="Fireworks over Paris" />
			<p lang="fr">
				Bonne année !
			</p>
		</div>
	</body>
</html>

Passed Example 4

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This span element has a lang attribute value of fr (French), which matches one of its most common languages. The most common languages are both English and French because all the words belong to both languages.

<html lang="en">
	<p>
		Even though all its words are English and it has meaning in English, the sentence
		<span lang="fr">Paul put dire comment on tape</span> is also a French sentence.
	</p>
</html>

Passed Example 5

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This span element has a lang attribute value of en (English), which matches one of its most common languages. The most common languages are both English and French because all the words belong to both languages.

<html lang="fr">
	<p>
		Bien que tous les ses mots soient français et qu'elle ait un sens en français, la phrase
		<span lang="en">Paul put dire comment on tape</span> est aussi une phrase anglaise.
	</p>
</html>

Failed

Failed Example 1

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This span element has lang attribute value of fr (French), which does not match its most common language. The most common language is Dutch because all words are Dutch.

<html lang="en">
	<head>
		<title>Dutch idioms</title>
	</head>
	<body>
		<p>
			The Dutch phrase <span lang="fr">"Hij ging met de kippen op stok"</span> literally translates into "He went to
			roost with the chickens", but it means that he went to bed early.
		</p>
	</body>
</html>

Failed Example 2

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The second p element has lang attribute value of en (English), which does not match its most common language. The most common language is Dutch because all English words are in span elements with a lang attribute value of fr. Both span elements also have an incorrect lang attribute in order to make sure that all targets in this example fail the rule.

<html lang="nl">
	<head>
		<title>Met de kippen op stok</title>
	</head>
	<body>
		<blockquote>
			<p>"Hij ging met de kippen op stok"</p>
		</blockquote>
		<p lang="en">
			<span lang="fr">The Dutch phrase</span> "Hij ging met de kippen op stok"
			<span lang="fr"
				>literally translates into "He went to roost with the chickens", but it means that he went to bed early.</span
			>
		</p>
	</body>
</html>

Failed Example 3

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This div element has a lang attribute value of fr (French), which does not match its most common language. The most common language is English because the accessible texts are English, and all other text is in a p element with a lang attribute value of nl, which also doesn't match its common language.

<html lang="fr">
	<head>
		<title>Feu d'artifice du nouvel an</title>
	</head>
	<body>
		<div lang="fr">
			<img src="/test-assets/shared/fireworks.jpg" alt="Fireworks over Paris" />
			<p lang="nl">
				Bonne année !
			</p>
		</div>
	</body>
</html>

Failed Example 4

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This div element has a lang attribute value of fr (French), which does not match its most common language. The most common language is English because the accessible name of the img element is English. The lang attribute on the p element is effectively ignored. The p element is not applicable because there is no text inheriting its programmatic language from it since its content is neither visible nor included in the accessibility tree.

<html lang="fr">
	<head>
		<title>Feu d'artifice du nouvel an</title>
	</head>
	<body>
		<div lang="fr">
			<img src="/test-assets/shared/fireworks.jpg" aria-labelledby="caption" />
			<p lang="en" id="caption" hidden>
				Fireworks over Paris
			</p>
		</div>
	</body>
</html>

Inapplicable

Inapplicable Example 1

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There are no HTML elements in this document.

<svg xmlns="http://www.w3.org/2000/svg" lang="en">
    <text x="0" y="0">I love ACT rules!</text>
</svg>

Inapplicable Example 2

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

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

Inapplicable Example 3

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This p element has an invalid language tag.

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

Inapplicable Example 4

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There is no text inheriting its programmatic language from the first p element because it has no content.

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

Inapplicable Example 5

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There is no text inheriting its programmatic language from this p element because it has no content that is either visible or included in the accessibility tree.

<html lang="en">
	<body>
		<p lang="fr" hidden>I love ACT rules!</p>
	</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.

Accessibility Support for Accessible Name

  • Because the accessible name and description computation is not clear about which whitespace are considered, browsers behave differently when trimming and flattening the accessible name. For example, some browsers completely trim non-breaking spaces while some keep them in the accessible name.
  • There exists a popular browser which does not perform the same trimming and flattening depending whether the accessible name comes from content, an aria-label attribute, or an alt attribute.
  • There exists a popular browser which assign no accessible name (null) when none is provided, instead of assigned an empty accessible name ("").
  • The accessible name and description computation suggest that if an aria-labelledby attribute refers to an existing but empty element, the computation should stop and return an empty name without defaulting to the next steps. Several user agents and assistive technologies chose to use the next step in the computation in this case.

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.

Included in the accessibility tree

Elements included in the accessibility tree of platform specific accessibility APIs. Elements in the accessibility tree are exposed to assistive technologies, allowing users to interact with the elements in a way that meet 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.

Note: Users of assistive technologies might still be able to interact with elements that are not included in the accessibility tree. An example of this is a focusable element with an aria-hidden attribute with a value of true. Such an element could still be interacted using sequential keyboard navigation regardless of the assistive technologies used, even though the element would not be included in the accessibility tree.

Most Common Language of an Element

The most common language of an element is determined by counting the number of words in the text inheriting its programmatic language from this element that are part of any of the languages in the language subtag registry. The same word can be part of multiple languages. In case of ties, the element has several most common languages. If there are no words in the text inheriting its programmatic language from the element, then it has no most common language.

For more details, see examples of most common language.

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.

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:

An element F is an element inheriting its programmatic language from an element E if 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.

Valid Language Tag

A language tag is valid 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 BCP 47 language tag syntax, i.e. a sequence of subtags separated by hyphens, where a subtag is any sequence of alphanumerical characters. Thus, this definition intentionally differs from the strict BCP 47 syntax (and ABNF grammar) as user agents and assistive technologies are more lenient in what they accept. The definition is however consistent with the behavior of the :lang() pseudo-selector as defined by Selectors Level 3. For example, de-hello would be an accepted way to indicate German in current user agents and assistive technologies, despite not being valid according to BCP 47 grammar. As a consequence of this definition, however, grandfathered tags are not correctly recognized as valid language subtags.

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

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.


Useful Links


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. This section will not be included in the rule when it is published on the W3C website.

No Implementations

Implementation reports are not provided for this rule.

Acknowledgments

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