Reference: Language tags and codes

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This reference is based on family of standards ISO-639 Codes for the representation of names of languages:

  • ISO 639-1 - Part 1: Alpha-2 code
    • two-character code
    • registration authority: International Information Centre for Terminology
  • ISO 639-2 - Part 2: Alpha-3 code
    • contains 2 sets of codes (code in both sets are identical in majority of cases):
      • 639-2/B - bibliographic applications
      • 639-2/T - terminology applications
    • registration authority: The Library of Congress
  • ISO 639-3 - Part 3: Alpha-3 code for comprehensive coverage of languages
    • aims to define three-letter identifiers for all known human languages
    • Registration authority: SIL International


  • RFC 5646 (BCP 47): Tags for Identifying Languages (obsoletes RFC 4646 - RFC 3066 - RFC 1766)
    • language tags and subtags are case insensitive, but it is recommended to use existing conventions
    • individual subtags are separated by hyphen "-"
    • language tag consist of several subtags:
      1. language subtag
        • cannot be omitted
        • if ISO 639-1 exists it is used
        • if ISO 639-2/B a 639-2/T differ then 639-2/T is used
      2. extended language subtags
        • based on ISO 639-3
      3. script subtag
        • must follow any primary and extended language subtags and precede any other tags
        • 4 letter codes based on ISO 15924 - Information and documentation -- Codes for the representation of names of scripts
        • at most one script subtag allowed; should be omitted if it does not add some distinguishing value
      4. region subtag
        • must follow any primary, extended language and script subtags and precede all others
        • 2 letter region subtags according to ISO 3166-1 - Codes for the representation of names of countries and their subdivisions -- Part 1: Country codes
        • 3 letter region subtags consist of digits; based on UN Standard Country or Area Codes for Statistical Use
      5. variant subtags
        • if they begin with a letter (a-z; A-Z) must be at least 5 characters long
        • if they begin with a digit (0-9) must be at least 4 characters long
      6. extension subtags
      7. private use subtags

Prepared by: Miloslav Nic (Mila)

Reference: Language tags and codes

starts with contains (at least 3 characters needed)