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:
- has a
langattribute that is neither empty (“”) nor only ASCII whitespace; and - is in a top-level browsing context; and
- has a node document with a content type of
text/html.
Expectation
For each test target, the lang attribute has a known primary language tag.
Assumptions
-
The language of the page can be set by other methods than the
langattribute, for example using HTTP headers or themetaelement. 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. -
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 3.1.1 Language of Page; this notably excludes grandfathered tags and ISO 639.2 three-letters codes, both having poor support in assistive technologies.
Accessibility Support
There are no major accessibility support issues known for this rule.
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.
Related rules
Bibliography
- Understanding Success Criterion 3.1.1: Language of Page
- H57: Using language attributes on the html element
- RFC 5646: Tags for Identifying Languages
- The
langandxml:langattributes
Accessibility Requirements Mapping
3.1.1 Language of Page (Level A)
- Learn more about 3.1.1 Language of Page
- Required for conformance to WCAG 2.0 and later on level A and higher.
- Outcome mapping:
- Any
failedoutcomes: success criterion is not satisfied - All
passedoutcomes: success criterion needs further testing - An
inapplicableoutcome: success criterion needs further testing
- Any
H57: Using language attributes on the html element
- Learn more about technique H57
- Not required for conformance to any W3C accessibility recommendation.
- Outcome mapping:
- Any
failedoutcomes: technique is not satisfied - All
passedoutcomes: technique needs further testing - An
inapplicableoutcome: technique needs further testing
- Any
Input Aspects
The following aspects are required in using this rule.
Test Cases
Passed
Passed Example 1
This html element has a lang attribute with a known primary language tag.
<html lang="FR"></html>
Passed Example 2
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
This html element has a lang attribute with a known primary language tag.
<html lang="em-US"></html>
Failed Example 2
This html element has a lang attribute with a known primary language tag.
<html lang="#1"></html>
Failed Example 3
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
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
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:
- 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.
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 | Consistency | Complete | Report |
|---|---|---|---|
| Alfa | Consistent | Yes | View Report |
| Axe-core | Consistent | Yes | View Report |
| QualWeb | Consistent | Yes | View Report |
| SortSite | Consistent | Yes | View Report |
Changelog
This is the first version of this ACT rule.