Proposed HTML page lang and xml:lang attributes have matching values
Deprecated
This rule has been deprecated, as modern screen readers no longer use xml:lang when the lang attribute is given, regardless of which MIME type the page is served with. This rule is not maintained anymore and should not be used.
Description
This rule checks that both lang and xml:lang attributes on the root element of a non-embedded HTML page, have the same primary language subtag.
Applicability
This rule applies to any document element if it is an html element for which all the following are true:
- is in a top-level browsing context; and
- has a node document with a content type of
text/html; and - has a
langattribute with a known primary language tag; and - has a non-empty
xml:langattribute.
Expectation
For each test target, the values of the primary language subtags, if any exist, for the lang and xml:lang attributes are the same.
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.
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.
-
The rule assumes that having
langandxml:langattributes with matching primary language subtags but non-matching language tags overall, will not cause accessibility issues. This is not necessarily the case for all languages. One notable case is the language tags for Cantonese (zh-yue) and Mandarin (zh-cmn) where the primary language subtags match, but the extended language subtags don’t. Such a case would not fail this rule, but could lead to accessibility issues.
Accessibility Support
Since most assistive technologies will consistently use lang over xml:lang when both are used, violation of this rule may not necessarily be a violation of WCAG 2. Only when there are inconsistencies between assistive technologies as to which attribute is used to determine the language does this lead to a violation of SC 3.1.1.
Bibliography
- 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
Input Aspects
The following aspects are required in using this rule.
Test Cases
Passed
Passed Example 1
This html element has identical primary language subtags for its lang and xml:lang attributes.
<html lang="EN" xml:lang="en"></html>
Passed Example 2
This html element has identical primary language subtags for its lang and xml:lang attributes. The extended language subtags also match.
<html lang="en-GB" xml:lang="en-GB"></html>
Passed Example 3
This html element has identical primary language subtags for its lang and xml:lang attributes. The extended language subtags do not match, but this is not required by this rule.
<html lang="en-GB" xml:lang="en-US"></html>
Failed
Failed Example 1
This html element has different primary language subtags for its lang and xml:lang attributes.
<html lang="fr" xml:lang="en"></html>
Failed Example 2
This html element has different primary language subtags for its lang and xml:lang attributes. The extended language subtags do match, but this rules only focus on the primary language subtags.
<html lang="fr-CA" xml:lang="en-CA"></html>
Inapplicable
Inapplicable Example 1
This rule does not apply to svg elements.
<svg xmlns="http://www.w3.org/2000/svg" lang="en" xml:lang="en"></svg>
Inapplicable Example 2
This rule does not apply to svg elements, even inside an html element.
<html>
<body>
<svg lang="en"></svg>
</body>
</html>
Inapplicable Example 3
This rule does not apply to math elements.
<math xml:lang="en"></math>
Inapplicable Example 4
This rule only applies to documents with a content type of text/html
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html lang="en" xml:lang="en"></html>
Inapplicable Example 5
This rule does not apply to html elements without an xml:lang attribute.
<html lang="en"></html>
Inapplicable Example 6
This rule applies neither to html elements without an xml:lang attribute, nor to html in nested browsing context
<html lang="en">
<iframe srcdoc="<html lang='en' xml:lang='en'></html>" />
</html>
Inapplicable Example 7
This rule does not apply to html elements with an empty ("") xml:lang attribute.
<html lang="fr" xml:lang=""></html>
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
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 five 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
- cantTell: Whether the rule is applicable, or not all expectations were met could not be fully determined by the tester.
- Untested: The tester has not attempted to evaluate the test subject.
Note: A rule has one passed or failed outcome for every test target. When a tester evaluates a test target it can also be reported as cantTell if the rule cannot be tested in its entirety. For example, when applicability was automated, but the expectations have to be evaluated manually.
When there are no test targets the rule has one inapplicable outcome. If the tester is unable to determine whether there are test targets there will be one cantTell outcome. And when no evaluation has occurred the test target has one untested outcome. This means that each test subject always has one or more outcomes.
Outcomes used in ACT Rules can be expressed using the outcome property of the [EARL10-Schema][].
Rule Versions
This is the first version of this ACT rule.