Document Language

Requirement

WCAG 2.1 Success Criterion 3.1.1, Language of Page (Level A), states: “The default human language of each Web page can be programmatically determined.” W3C technique PDF16 describes meeting it for PDF files by setting the /Lang entry in the document catalog.

There are several places a language can be declared, and it is sometimes practical to set it in more than one, such as the lang attribute on the html element, the /Lang entry in a PDF, or the language settings stored in the XML inside a Microsoft Office document. Most authoring tools handle this. The key point is to assign a valid BCP 47 language tag, the IETF standard built on ISO language and country codes. For U.S. governments that publish primarily in English, en-US or en is the correct value for the vast majority of documents.

Distinctions

• Declared vs. assumed. When no language is declared, most screen readers fall back to the user’s own configured language, so an English document often reads correctly for an English-speaking user. The requirement is still unmet, because the language is not programmatically determined from the document.
• Legacy formats. Older formats, including WordPerfect 6.0a, had no language attribute. For these, an organization-wide default or an algorithmically detected language can supply the value.

Sources

• Understanding Success Criterion 3.1.1: Language of Page, W3C Web Accessibility Initiative. Retrieved September 23, 2026.
• PDF16: Setting the default language using the /Lang entry in the document catalog of a PDF document, W3C Web Accessibility Initiative. Retrieved September 23, 2026.
• Declaring language in HTML, W3C Internationalization. Retrieved September 24, 2026.