About This Accessibility Rule
Screen readers rely on language information to select the correct pronunciation engine for content. Each language has its own sound library with unique pronunciation rules, intonation, and phonetic patterns. When a screen reader encounters a lang attribute with a valid value, it seamlessly switches to the appropriate library. But when the value is invalid — for example, lang="egnlish" instead of lang="en" — the screen reader cannot identify the language and falls back to its default, reading the foreign-language text with completely wrong pronunciation.
This primarily affects blind users and deafblind users who depend on screen readers, as well as users with cognitive disabilities who may rely on text-to-speech tools. Imagine hearing Spanish text pronounced with English phonetic rules — it would be nearly incomprehensible.
Note that this rule specifically checks lang attributes on elements within the page (not the <html> element itself, which is covered by a separate rule). It applies whenever you use the lang attribute to indicate that a section of content is in a different language than the rest of the page.
Related WCAG Success Criteria
This rule maps to WCAG 2.0 / 2.1 / 2.2 Success Criterion 3.1.2: Language of Parts (Level AA). This criterion requires that the human language of each passage or phrase in the content can be programmatically determined, except for proper names, technical terms, and words of indeterminate language. Using a valid language code is essential to meeting this requirement — an invalid code fails to programmatically convey the language.
This rule is also referenced by the Trusted Tester methodology, EN 301 549, and RGAA.
How to Fix It
-
Use valid language codes. Language values must conform to the BCP 47 standard. In practice, this means using two- or three-letter codes from the IANA Language Subtag Registry. Common examples include
en(English),fr(French),es(Spanish),de(German),zh(Chinese),ar(Arabic), andja(Japanese). -
Check for typos. Invalid values are often caused by misspellings (e.g.,
lang="enlish") or using full language names instead of codes (e.g.,lang="French"instead oflang="fr"). -
Use dialect subtags when appropriate. You can specify regional variants such as
en-US(American English),en-GB(British English), orfr-CA(Canadian French). The primary subtag alone is also valid. -
Set the
dirattribute for RTL languages. If you’re marking content in a right-to-left language like Arabic or Hebrew, pair thelangattribute withdir="rtl"to ensure correct text rendering.
Examples
Incorrect: Invalid language code
<p>Welcome to our site. <span lang="spn">Bienvenidos a nuestro sitio.</span></p>
The value spn is not a valid language subtag. Screen readers cannot identify this as Spanish.
Incorrect: Full language name instead of code
<p>Here is a quote: <q lang="Japanese">素晴らしい</q></p>
The value Japanese is not a valid BCP 47 language code.
Correct: Valid two-letter language code
<p>Welcome to our site. <span lang="es">Bienvenidos a nuestro sitio.</span></p>
The value es is the valid language subtag for Spanish.
Correct: Valid language code with regional subtag
<p>The Canadian term is <span lang="fr-CA">dépanneur</span>.</p>
The value fr-CA correctly identifies Canadian French.
Correct: RTL language with direction attribute
<p>The Arabic word for peace is <span lang="ar" dir="rtl">سلام</span>.</p>
The value ar is the valid subtag for Arabic, and dir="rtl" ensures proper text directionality.
Correct: Multiple language switches on one page
<p>
In English we say "goodbye," in German it's
<span lang="de">Auf Wiedersehen</span>, and in Japanese it's
<span lang="ja">さようなら</span>.
</p>Each inline element uses a valid language code, allowing the screen reader to switch pronunciation engines as needed.
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