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Proposed HTML page lang attribute has valid language tag

Description

This rule checks that the lang attribute of the root element of a non-embedded HTML page has a language tag with a known primary language subtag.

Applicability

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

Expectation

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

Assumptions

Accessibility Support

There are no accessibility support issues known.

Background

This rule is only applicable to non-embedded HTML pages. HTML pages embedded into other documents, such as through iframe or object elements are not applicable because they are not web pages according to the definition in WCAG.

Bibliography

Accessibility Requirements Mapping

Input Aspects

The following aspects are required in using this rule.

Test Cases

Passed

Passed Example 1

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This html element has a lang attribute with a known primary language tag.

<html lang="FR"></html>

Passed Example 2

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This html element has a lang attribute with a known primary language tag even though the region subtag is not.

<html lang="en-US-GB"></html>

Failed

Failed Example 1

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This html element has a lang attribute with a known primary language tag.

<html lang="em-US"></html>

Failed Example 2

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This html element has a lang attribute with a known primary language tag.

<html lang="#1"></html>

Failed Example 3

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

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

Failed Example 4

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

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

Inapplicable

Inapplicable Example 1

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This rule does not apply to svg elements.

<svg xmlns="http://www.w3.org/2000/svg" lang="fr"></svg>

Glossary

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.

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:

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.

Rule Versions

  1. Proposed version, 21 June 2022 (compare)
  2. Latest 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 Report
Alfa (fully automated) 0.57.2 Automated tool Consistent Alfa (fully automated) Report
Alfa (semi-automated) 0.57.2 Semi-automated tool Consistent Alfa (semi-automated) Report
Axe DevTools Pro 4.37.1 Semi-automated tool Consistent Axe DevTools Pro Report
Axe-core 4.8.1 Automated tool Consistent Axe-core Report
Equal Access Accessibility Checker 3.1.42-rc.0 Automated tool Consistent Equal Access Accessibility Checker Report
QualWeb 3.0.0 Automated tool Consistent QualWeb Report
SortSite 6.45 Automated tool Consistent SortSite Report
Total Validator 17.1.0 Linter Consistent Total Validator Report
Total Validator (+Browser) 17.3.0 Automated tool Consistent Total Validator (+Browser) Report
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