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An IETF BCP 47 language tag is a a standardized code or tag that is used to identify human languages in internet programming as used by computing standards such as HTTP, HTML, XML and PNG.. The tag structure has been standardized by the Internet Engineering Task Force (IETF) in Best Current Practice (BCP) 47; the subtags are maintained by the IANA Language Subtag Registry. To distinguish language variants for countries, regions, or writing systems, IETF language tags combine subtags from other standards such as ISO 639, ISO 15924, ISO 3166-1 and UN M.49.
Notably,[why?] the tag en stands for English; es-419 for Latin American Spanish; rm-sursilv for Sursilvan; gsw-u-sd-chzh for Zürich German; nan-Hant-TW for Min Nan Chinese as spoken in Taiwan using traditional Han characters.