RFC 1766 (rfc1766) - Page 2 of 9

Tags for the Identification of Languages

RFC 1766                      Language Tag                    March 1995


2.  The Language tag

   The language tag is composed of 1 or more parts: A primary language
   tag and a (possibly empty) series of subtags.

   The syntax of this tag in RFC-822 EBNF is:

    Language-Tag = Primary-tag *( "-" Subtag )
    Primary-tag = 1*8ALPHA
    Subtag = 1*8ALPHA

   Whitespace is not allowed within the tag.

   All tags are to be treated as case insensitive; there exist
   conventions for capitalization of some of them, but these should not
   be taken to carry meaning.

   The namespace of language tags is administered by the IANA according
   to the rules in section 5 of this document.

   The following registrations are predefined:

   In the primary language tag:

    -    All 2-letter tags are interpreted according to ISO standard
         639, "Code for the representation of names of languages" [ISO
         639].

    -    The value "i" is reserved for IANA-defined registrations

    -    The value "x" is reserved for private use. Subtags of "x"
         will not be registered by the IANA.

    -    Other values cannot be assigned except by updating this
         standard.

   The reason for reserving all other tags is to be open towards new
   revisions of ISO 639; the use of "i" and "x" is the minimum we can do
   here to be able to extend the mechanism to meet our requirements.

   In the first subtag:

    -    All 2-letter codes are interpreted as ISO 3166 alpha-2
         country codes denoting the area in which the language is
         used.

    -    Codes of 3 to 8 letters may be registered with the IANA by
         anyone who feels a need for it, according to the rules in



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