Element with lang attribute has valid language tag

  • Rule Type:atomic
  • Rule Id: de46e4
  • Last modified: Dec 18, 2020
  • 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 to 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.

Description

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

Applicability

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

Expectation

For each test target, the lang attribute value is a valid 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 valid language tags even if these do not conform to the BCP 47 syntax.
  • This rule assumes that grandfathered tags are not used as these will not be recognized as valid language tags.

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

Test Cases

Passed

Passed Example 1

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This article element has a lang attribute value which is not empty ("") and has a valid language tag.

<html>
	<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 is not empty ("") and has a valid language tag. The region section in the value is ignored by the rule (and the definition of valid language tag).

<html>
	<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 valid language tag, but a syntactically invalid region subtag which is ignored by the rule.

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

Failed

Failed Example 1

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

<html>
	<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 is not a valid language tag.

<html>
	<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 is not a valid language tag.

<html>
	<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. The lang attribute must be valid because the content is visible.

<html>
	<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, and its descendant is not visible though it is still included in the accessibility tree.

<html>
	<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>

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>

Glossary

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.

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.

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.

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)

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.

ToolConsistencyCompleteReport
QualWebconsistentYesView Report

Acknowledgments

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