# HTML: `lang` Use an "IETF BCP 47 Language Tag"; for example: * `en`: English * `zh-Hant`: Chinese, written in the Traditional Chinese script # References [3.2.5.2. The lang and xml:lang attributes](https://www.w3.org/TR/2021/SPSD-html52-20210128/dom.html#the-lang-and-xmllang-attributes): > The lang attribute (in no namespace) specifies the primary language > for the element’s contents and for any of the element’s attributes > that contain text. Its value must be a valid BCP 47 language tag, or > the empty string. Setting the attribute to the empty string indicates > that the primary language is unknown. [BCP47] [BCP47](https://www.w3.org/TR/2021/SPSD-html52-20210128/references.html#biblio-bcp47): > A. Phillips; M. Davis. Tags for Identifying Languages. September 2009. > IETF Best Current Practice. URL: <https://tools.ietf.org/html/bcp47> [BCP 47](https://www.rfc-editor.org/info/bcp47): > RFC 5646, BCP 47 > > Tags for Identifying Languages [RFC 5646](https://www.rfc-editor.org/info/rfc5646): > IANA Language Subtag Registry [2.1. Syntax](https://www.rfc-editor.org/rfc/rfc5646.html#section-2.1). [Appendix A. Examples of Language Tags (Informative)](https://www.rfc-editor.org/rfc/rfc5646.html#appendix-A). [IANA Language Subtag Registry](https://www.iana.org/assignments/language-subtag-registry/language-subtag-registry).
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