HTML page language subtag matches default language
Applicability
This rule applies to any [document element][] if it is an html element for which all of the following are true:
The [document element][] has a lang attribute with a value that has a [known primary language tag][]; and
The [document element][] is in a [top-level browsing context][]; and
The [document element][] has a [content type][] of text/html; and
The [document element][] has a defined [default page language][].
Expectation
For each test target, the [known primary language tag][] of its lang attribute matches the [default page language][] of the test target.
Assumptions
This rule assumes that the default human language of a page, as described in WCAG 2, can be determined by counting the number of words used in each language. If the default language needs to be derived in some other way (such as frequency analysis, mutual information based distance, …), this rule may fail while Success Criterion 3.1.1: Language of Page is still satisfied.
The language of the page can be set by other methods than the lang attribute, for example using HTTP headers or the meta element. 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][known primary language tag] even if these do not conform to the [RFC 5646][] syntax.
This rule assumes that only [known primary language tags][known primary language tag] are enough to satisfy [Success Criterion 3.1.1 Language of Page][sc311]; this notably excludes [grandfathered tags][] and [ISO 639.2][] three-letters codes, both having poor support in assistive technologies.
This rule assumes that iframe title elements are not exposed to assistive technologies and so does not consider them as part of the [default page language][].
This page has a lang [attribute value][] of en (English), which matches the [default language of the page][default page language]. The default language is English because all words are English.
<html lang="en">
<head>
<title>ACT Rules Format 1.0 - Abstract</title>
</head>
<body>
<p>
The Accessibility Conformance Testing (ACT) Rules Format 1.0 defines a format for writing accessibility test
rules. These test rules can be used for developing automated testing tools and manual testing methodologies. It
provides a common format that allows any party involved in accessibility testing to document and share their
testing procedures in a robust and understandable manner. This enables transparency and harmonization of testing
methods, including methods implemented by accessibility test tools.
</p>
</body>
</html>
Passed Example 2
This page has a lang attribute value of en (English), which matches the [default language of the page][default page language]. The default language is English because all but a few words are English.
<html lang="EN">
<head>
<title>Gelukkig</title>
</head>
<body>
<p>The Dutch word "gelukkig" has no equivalent in English.</p>
</body>
</html>
Passed Example 3
This page has lang attribute value of nl (Dutch), which matches the [default language of the page][default page language]. The default language is Dutch because all English words are in a p element with a lang attribute value of en.
<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">
This Dutch phrase literally translates into "He went to roost with the chickens", but it means that he went to bed
early.
</p>
</body>
</html>
Passed Example 4
This page has a lang attribute value of en (English), which matches the [default language of the page][default page language]. The default 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.
This page has a lang attribute value of da (Danish), which does not match the [default language of the page][default page language]. The default language is English because all words are English.
<html lang="da">
<head>
<title>ACT Rules Format 1.0 - Abstract</title>
</head>
<body>
<p>
The Accessibility Conformance Testing (ACT) Rules Format 1.0 defines a format for writing accessibility test
rules. These test rules can be used for developing automated testing tools and manual testing methodologies. It
provides a common format that allows any party involved in accessibility testing to document and share their
testing procedures in a robust and understandable manner. This enables transparency and harmonization of testing
methods, including methods implemented by accessibility test tools.
</p>
</body>
</html>
Failed Example 2
This page has a lang attribute value of nl (Dutch), which does not match the [default language of the page][default page language]. The default language is English because all but a few words are English.
<html lang="nl">
<head>
<title>Gelukkig</title>
</head>
<body>
<p>The Dutch word "gelukkig" has no equivalent in English.</p>
</body>
</html>
Failed Example 3
This page has a lang attribute value of en (English), which does not match the [default language of the page][default page language]. The default language is Dutch because all English words are in a p element with a lang attribute value of en.
<html lang="en">
<head>
<title>Met de kippen op stok</title>
</head>
<body>
<blockquote>
<p>"Hij ging met de kippen op stok"</p>
</blockquote>
<p lang="en">
This Dutch phrase literally translates into "He went to roost with the chickens", but it means that he went to bed
early.
</p>
</body>
</html>
Failed Example 4
This page has a lang attribute value of nl (Dutch), which does not match the [default language of the page][default page language]. The default 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.
This page has a lang attribute value of nl (Dutch), which does not match the [default language of the page][default page language]. The default language is English because the accessible name of the img element is English. The lang attribute on the p element is effectively ignored.
This page has an undefined [default language][default page language] because it has no content or [document title][].
<html></html>
Inapplicable Example 3
This page has an undefined [default language][default page language] because it has no [document title][] and all its content is wrapped in an element with a lang attribute.
<html>
<p lang="en">
The Accessibility Conformance Testing (ACT) Rules Format 1.0 defines a format for writing accessibility test rules.
These test rules can be used for developing automated testing tools and manual testing methodologies. It provides a
common format that allows any party involved in accessibility testing to document and share their testing procedures
in a robust and understandable manner. This enables transparency and harmonization of testing methods, including
methods implemented by accessibility test tools.
</p>
</html>
Inapplicable Example 4
This page has an undefined [default language][default page language] because it can either be English or French.
<html lang="fr">
<head>
<title>Paul put dire comment on tape</title>
</head>
<body>
<p>Paul put dire comment on tape</p>
</body>
</html>
Inapplicable Example 5
The lang [attribute value][] of this page is an [iso 639.2][] three letters code, hence has no [known primary language tag][].
<html lang="eng">
<body>
<p lang="en">I love ACT rules!</p>
</body>
</html>
Inapplicable Example 6
The lang [attribute value][] of this page is a [grandfathered tag][grandfathered tags], hence has no [known primary language tag][].
<html lang="i-lux">
<body>
<p lang="lb">Lëtzebuerg ass e Land an Europa.</p>
</body>
</html>
