Network Working GroupA. Phillips, Ed.
Internet-DraftwebMethods, Inc.
Expires: October 7, 2004M. Davis
 April 8, 2004

Tags for Identifying Languages


Status of this Memo

This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026.

Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts.

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This Internet-Draft will expire on October 7, 2004.

Copyright Notice

Copyright (C) The Internet Society (2004). All Rights Reserved.


This document describes a language tag for use in cases where it is desired to indicate the language used in an information object, how to register values for use in this language tag, and a construct for matching such language tags, including user defined extensions for private interchange.

Table of Contents

1.  Introduction
2.  The Language Tag
2.1  Syntax
2.2  Language Tag Sources
2.2.1  Pre-Existing RFC3066 Registrations
2.2.2  Possibilities for Registration
2.3  Choice of Language Tag
2.4  Meaning of the Language Tag
2.4.1  Language Range
2.4.2  Matching Language Tags
3.  IANA Considerations
3.1  Registration Procedure for Subtags
4.  Security Considerations
5.  Character Set Considerations
6.  Changes from RFC3066
§  References
§  Authors' Addresses
A.  Acknowledgements
B.  Examples of Language Tags (Informative)
§  Intellectual Property and Copyright Statements


1. Introduction

Human beings on our planet have, past and present, used a number of languages. There are many reasons why one would want to identify the language used when presenting or requesting information.

Information about a user's language preferences commonly needs to be identified so that appropriate processing can be applied. For example, the user's language preferences in a brower can be used to select web pages appropriately. A choice of language preference can also be used to select among tools (such as dictionaries) to assist in the processing or understanding of content in different langauges.

In addition, knowledge about the particular language used by some piece of information content may be useful or even required by some types of information processing; for example spell-checking, computer-synthesized speech, Braille transcription, or high-quality print renderings.

One means of indicating the language used is by labeling the information content with a language identifier. These identifiers can also be used to specify user preferences when selecting information content, or for labeling additional attributes of content and associated resources.

These identifiers can also be used to indicate additional attributes of content that are closely related to the language. In particular, it is often necessary to indicate specific information about the dialect, writing system, or orthography used in a document or resource, as these attributes may be important for the user to obtain information in a form that they can understand, or important in selecting appropriate processing resources for the given content.

This document specifies an identifier mechanism, a registration function for values to be used with that identifier mechanism, and a construct for matching against those values. It also defines a mechanism for private use extension and how private use, registered values, and matching interact.

The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC 2119][10].


2. The Language Tag

2.1 Syntax

The language tag is composed of one or more parts: A primary language subtag and a (possibly empty) series of subsequent subtags. Subtags are distinguished by their length and content, so that each type of subtag can be recognized solely by these features. This makes it possible to construct a parser that can extract and assign some semantic information to the subtags, even if specific subtag values are not recognized.

The syntax of this tag in ABNF [RFC 2234][11] is:

= lang *["-s-" extlang] ["-" script] ["-" region] *["-" variant] ["-x" extensions]
=/ "x" extensions ; private use tag
=/ grandfathered-registrations
lang    = 2*3 ALPHA  ; shortest ISO 639 tag
        =/ registered-lang
extlang = 2*15 ALPHA ; additional language subtag
script  = 4 ALPHA    ; ISO 15924 tag
region  = 2 ALPHA    ; ISO 3166 tag
        =/ 3 DIGIT   ; UN country number
variant =  5*15 alphanum
extensions      = 1* ("-" value) ; private use extensions
value           = 1*32 alphanum
registered-lang = 5*15 alphanum
grandfathered-registrations = ALPHA * (alphanumdash)
alphanum     = (ALPHA / DIGIT)
alphanumdash = (alphanum / "-")

 Language Tag ABNF 

The character "-" is HYPHEN-MINUS (ABNF: %x2D).

The tags and their subtags, including private use extensions, are to be treated as case insensitive: there exist conventions for the capitalization of some of them, but these should not be taken to carry meaning. For instance, [ISO 3166][4] recommends that country codes be capitalized (MN Mongolia), while [ISO 639][3] recommends that language codes be written in lower case (mn Mongolian). In the language tags defined by this document, however, the tag 'mn-MN' is not distinct from 'MN-mn' or 'mN-Mn' (or any other combination) and each of these variations conveys the same meaning.

For examples of language tags, see Appendix B at the end of this document.

2.2 Language Tag Sources

The namespace of language tags and their subtags is administered by the Internet Assigned Numbers Authority (IANA) [15] according to the rules in Section 3.1.

Terminology in this section:

The rules in this section apply to the various subtags within the language tags defined in this document, excepting those "grandfathered" tags defined in Section 2.2.1.

Note that registered subtags can only appear in specific positions in a tag. Specifically, they can only occur as primary (language) subtags, as extended language subtags delmited with the single letter subtag "s" or as variant subtags.

In addition, private use subtags may only occur at the end of the sequence of subtags and will not be interspersed with subtags defined in the rules that follow.

Each subtag type has unique length and content restrictions that make identification of the subtag's type possible, even if the content of the subtag itself is unrecognized. This allows tags to be parsed and processed without reference to the latest version of the underlying standards or the IANA registry and it makes the associated exception handling when parsing tags simpler.

Single letter and digit subtags are reserved for current or future use. These include the following current uses:

The primary subtag is the first subtag in a language tag and cannot be empty. Except as noted, the primary subtag is the "language" subtag. The following rules apply to the assignment and interpretation of the primary subtag:

The following rules apply to the extended language subtags:

The following rules apply to the script subtags:

The following rules apply to the region subtags:

The following rules apply to the variant subtags:

The following rules apply to private use extensions:

For example: Users who wished to utilize SIL Ethonologue for identification might agree to exchange tags such as 'az-Arab-x-AZE-derbend'. This example contains two extension subtags. The first is "AZE" and the second is "derbend".

2.2.1 Pre-Existing RFC3066 Registrations

Existing IANA registered language tags from RFC1766/RFC3066 that are not defined by additions to this document maintain their validity. IANA will maintain these tags, adding a notation that they are "grandfathered from RFC 3066".

The rules governing existing RFC 1766 and RFC 3066 registered tags are:

Users of tags that are grandfathered should consider registering appropriate subtags using the new format (but are not required to).

2.2.2 Possibilities for Registration

Possibilities for registration of subtags include:

This document leaves the decision on what subtags are appropriate or not to the registration process described in Section 3.1.

ISO 639 defines a maintenance agency for additions to and changes in the list of languages in ISO 639. This agency is:

International Information Centre for Terminology (Infoterm)
Aichholzgasse 6/12, AT-1120
Wien, Austria
Phone: +43 1 26 75 35 Ext. 312 Fax: +43 1 216 32 72

ISO 639-2 defines a maintenance agency for additions to and changes in the list of languages in ISO 639-2. This agency is:

Library of Congress
Network Development and MARC Standards Office
Washington, D.C. 20540 USA
Phone: +1 202 707 6237 Fax: +1 202 707 0115

The maintenance agency for ISO 3166 (country codes) is:

ISO 3166 Maintenance Agency
c/o International Organization for Standardization
Case postale 56
CH-1211 Geneva 20 Switzerland
Phone: +41 22 749 72 33 Fax: +41 22 749 73 49

The registration authority for ISO 15924 (script codes) is:

Unicode Consortium Box 391476
Mountain View, CA 94039-1476, USA

The Statistics Division of the United Nations Secretariat maintains the Standard Country or Area Codes for Statistical Use and can be reached at:

Statistical Services Branch
Statistics Division
United Nations, Room DC2-1620
New York, NY 10017, USA

Fax: +1-212-963-0623

2.3 Choice of Language Tag

One may occasionally be faced with several possible tags for the same body of text.

Interoperability is best served if all users send the same tag, and use the same tag for the same language for all documents. If an application has requirements that make the rules here inapplicable, the application protocol specification MUST specify how the procedure varies from the one given here.

The text below is based on the set of tags known to the tagging entity.

  1. Use as precise a tag as possible, but no more specific than is justified. For example, 'de' might suffice for tagging an email written in German, while 'de-CH-1996' is probably unnecessarily precise for such a task.
  2. Avoid using subtags that add no distinguishing information about the content. For example, the script subtag in 'en-Latn-US' is generally unnecessary, since nearly all English texts are written in the Latin script.
  3. When a language has both an ISO 639-1 2-character code and an ISO 639-2 3-character code, you MUST use the ISO 639-1 2-character code.
  4. When a language has no ISO 639-1 2-character code, and the ISO 639- 2/T (Terminology) code and the ISO 639-2/B (Bibliographic) codes differ, you MUST use the Terminology code. NOTE: At present all languages that have both kinds of 3-character code also are assigned a 2-character code, and the displeasure of developers about the existence of two different code sets has been adequately communicated to ISO. So this situation will hopefully not arise.
  5. You SHOULD NOT use the UND (Undetermined) code unless the protocol in use forces you to give a value for the language tag, even if the language is unknown. Omitting the tag is preferred.
  6. You SHOULD NOT use the MUL (Multiple) tag if the protocol allows you to use multiple languages, as is the case for the Content-Language header in HTTP.
    NOTE: In order to avoid versioning difficulties in applications such as that experienced in RFC 1766[8], the ISO 639 Registration Authority Joint Advisory Committee (RA-JAC) has agreed on the following policy statement:
    "After the publication of ISO/DIS 639-1 as an International Standard, no new 2-letter code shall be added to ISO 639-1 unless a 3-letter code is also added at the same time to ISO 639-2. In addition, no language with a 3-letter code available at the time of publication of ISO 639-1 which at that time had no 2-letter code shall be subsequently given a 2-letter code."
    This will ensure that, for example, a user who implements "haw" (Hawaiian), which currently has no 2-character code, will not find his or her data invalidated by eventual addition of a 2-character code for that language."
  7. To maintain backwards compatibility, there are two provisions to account for potential instability in ISO 639, 3166, and 15924 codes.
    a) Ambiguity.
    Beginning with these standards as of 1 January, 2003, in the event that ISO639, ISO3166, or ISO15924 assigns a code a new meaning or reassigns a deprecated code, the new use of the code is not permitted in language tags defined by this document.
    In the event that either ISO 639 or ISO 15924 assigns a new meaning to an existing code, the language subtag reviewer, as described in Section 3, shall prepare a proposal for entering in the IANA registry as soon as practical a variant or registered language subtag as a surrogate value for the new code. The form of the registered language subtag or variant subtag will be at the discretion of the language subtag reviewer and must conform to other restrictions on language or variant subtags in this document.
    In the event ISO 3166 assigns a new meaning to an existing code, then the language subtag reviewer, as described in Section 3, shall prepare a proposal for entering the appropriate numeric UN country code as an informative entry in the IANA registry.
    The normal registration process described in Section 3.1 of this document applies to the review and registration of the registered subtags described above. Note that these subtags should never be used in combination with the subtag type for which they are a surrogate. For example, a "region" variant subtag should not be used with a region subtag.
    For example:
    cs-CS (Czech for Czechoslovakia)
    sr-891 (Serbian for Serbia and Montenegro, using the UN country code)
    qx-Latn (hypothetical reassigned value 'qx')
    qx2003-Latn (hypothetical registered language subtag)
    b) Stability.
    All other ISO codes are valid, even if they have been deprecated. Some examples, current at the time this document was drafted, are listed below. Where a new equivalent code has been defined (given below on the right side after a tilde), implementations should treat these tags as identical.
    For example, some deprecated ISO 639 codes:
    iw ~ he
    in ~ id
    ji ~ yi
    For example, some deprecated ISO 3166 codes:
    TP ~ TL

2.4 Meaning of the Language Tag

The language tag always defines a language as spoken (or written, signed or otherwise signaled) by human beings for communication of information to other human beings. Computer languages such as programming languages are explicitly excluded.

If a language tag B contains language tag A as a prefix, then B is typically "narrower" or "more specific" than A. For example, 'zh-Hant-TW' is more specific than 'zh-Hant'.

This relationship is not guaranteed in all cases: specifically, languages that begin with the same sequence of subtags are NOT guaranteed to be mutually intelligible, although they may be. For example, the tag 'az' shares a prefix with both 'az-Latn' (Azerbaijani written using the Latin script) and 'az-Cyrl' (Azerbaijani written using the Cyrillic script). A person fluent in one script may not be able to read the other, even though the text might be identical. Content tagged as 'az' most probably is written in just one script and thus might not be intelligible to a reader familiar with the other script.

The relationship between the tag and the information it relates to is defined by the standard describing the context in which it appears. Accordingly, this section can only give possible examples of its usage.

2.4.1 Language Range

A Language Range is a set of languages whose tags all begin with the same sequence of subtags. The following definition of language-range is derived from HTTP/1.1[14].

language-range = language-tag / "*"

That is, a language-range has the same syntax as a language-tag, or is the single character "*" and implicitly assumes that there is a semantic relationship between tags that share the same subtag prefixes.

A language-range matches a language-tag if it exactly equals the tag, or if it exactly equals a prefix of the tag such that the first character following the prefix is "-".

The special range "*" matches any tag. A protocol which uses language ranges may specify additional rules about the semantics of "*"; for instance, HTTP/1.1 specifies that the range "*" matches only languages not matched by any other range within an "Accept-Language:" header.

As noted above, not all languages or content denoted by a specific language-range may be mutually intelligible and this use of a prefix matching rule does not imply that language tags are assigned to languages in such a way that it is always true that if a user understands a language with a certain tag, then this user will also understand all languages with tags for which this tag is a prefix. The prefix rule simply allows the use of prefix tags if this is the case.

2.4.2 Matching Language Tags

Implementations that are searching for content or otherwise matching language tags to a language-range [Section 2.4.1] may choose to assume that there is a semantic relationship between two tags that share common prefixes. This is called 'language tag fallback'. The most common implementations follow this pattern:

  1. When searching for content using language tag fallback, the language tag is progressively truncated from the end until a match is located. For example, starting with the tag 'en-US-boont', searchs or matches would first be performed with the whole tag, then with 'en-US', and finally with 'en'. This allows some flexibility in finding content in accordance with Rules 1 and 2 in Section 2.3; allows better maintenance; and usually provides better results when data is not available at a specific level of tag granularity or is sparsely populated (than if the default language for the system or content were used). Any implementation that uses this technique should ensure that appropriate data is available on each level.

    Tag to match: en-US-boont
    1. en-US-boont
    2. en-US
    3. en
     Default Fallback Pattern Example 

  2. Private Use Extensions are orthogonal to language tag fallback. By default, implementations should ignore private use extensions and follow the default fallback pattern (above). Thus matching the tag "en-US-boont-x-traditional" would be exactly the same as the example above.
  3. Implementations that choose to interpret one or more private use extension subtags can choose a different fallback pattern or use the private use extensions to interpret content in a different fashion.


3. IANA Considerations

This section deals with the registration of subtags for use in language tags defined by this document, in accordance with the requirements of RFC2434[13].

3.1 Registration Procedure for Subtags

The procedure given here MUST be used by anyone who wants to use a subtag not given an interpretation in Section 2.2 of this document or previously registered with IANA.

This procedure MAY also be used to register information with the IANA about a tag or subtag defined by this document, for instance if one wishes to make publicly available a reference to the definition for a language such as sgn-US (American Sign Language), or additional information about a registration previously made via this procedure.

Variant subtags MUST NOT be registered using the pattern 2 ALPHA * DIGIT to accommodate the provisions in Section 2.3, rule 7a of this document. That is, the subtag yx1234 can NOT be registered except under the aforementioned provisions.

Extended language subtags that are registered MUST be at least 4 characters long.

Subtags MUST NOT be registered that start with the letter 'x', since this prefix is reserved for Private Use subtags.

The process starts by filling out the registration form reproduced below.

Name of requester:
E-mail address of requester:
Subtag to be registered:
Type of Subtag: 
  [ ] language 
  [ ] extended language 
  [ ] variant
  [ ] region (informative; for use by language subtag reviewer only)
Full English name of subtag:
Intended meaning of the subtag:
If variant subtag, the intended prefix(es) of subtag:
If extended language subtag, the intended prefix(es) of subtag:
Native name of language (transcribed into ASCII):
Reference to published description of the language (book or article):
Any other relevant information:

The subtag registration form MUST be sent to <> for a two week review period before it can be submitted to IANA. (This is an open list. Requests to be added should be sent to <>.)

Variant subtags are generally registered for use with a particular prefix or set of prefixes. For example, the subtag 'boont' is intended for use with the prefix 'en-', since Boontling is a dialect of English. This information MUST be provided in the registration form.

Any registered subtag MAY be incorporated into a variety of language tags, according to the rules of Section 2.1. This makes validation simpler and thus more uniform across implementations, and does not require new registrations for different intended prefixes.

However, the intended prefixes for a given registered subtag will be maintained in the IANA registry as a guide to usage. If it is necessary to add an additional intended prefix to that list for an existing language tag, that can be done by filing an additional registration form. In that form, the "Any other relevant information: " field should indicate that it is the addition of an additional intended prefix.

When the two week period has passed, the subtag reviewer, who is appointed by the IETF Applications Area Director, either forwards the request to IANA@IANA.ORG, or rejects it because of significant objections raised on the list. Note that the reviewer can raise objections on the list himself, if he or she so desires. The important thing is that the objection must be made publicly.

The applicant is free to modify a rejected application with additional information and submit it again; this restarts the two week comment period.

Decisions made by the reviewer may be appealed to the IESG [RFC 2028][9] under the same rules as other IETF decisions [RFC 2026]. All registered forms are available online in the directory under "languages".

Updates of registrations follow the same procedure as registrations. The subtag reviewer decides whether to allow a new registrant to update a registration made by someone else; normally objections by the original registrant would carry extra weight in such a decision.

Registrations are permanent and stable. When some registered subtag should not be used any more, for instance because a corresponding ISO 639 code has been created, the registration should be amended by adding a remark like "DEPRECATED: use <new code> instead" to the "other relevant information" section.

Note: The purpose of the "published description" is intended as an aid to people trying to verify whether a language is registered, or what language a particular subtag refers to. In most cases, reference to an authoritative grammar or dictionary of that language will be useful; in cases where no such work exists, other well known works describing that language or in that language may be appropriate. The subtag reviewer decides what constitutes "good enough" reference material.


4. Security Considerations

The only security issue that has been raised with language tags since the publication of RFC 1766, which stated that "Security issues are believed to be irrelevant to this memo", is a concern with language ranges used in content negotiation - that they may be used to infer the nationality of the sender, and thus identify potential targets for surveillance.

This is a special case of the general problem that anything you send is visible to the receiving party. It is useful to be aware that such concerns can exist in some cases.

The evaluation of the exact magnitude of the threat, and any possible countermeasures, is left to each application protocol.


5. Character Set Considerations

Language tags may always be presented using the characters A-Z, a-z, 0-9, and HYPHEN-MINUS, which are present in most character sets, so presentation of language tags should not have any character set issues.

The issue of deciding upon the rendering of a character set based on the language tag is not addressed in this memo; however, it is thought impossible to make such a decision correctly for all cases unless means of switching language in the middle of a text are defined (for example, a rendering engine that decides font based on Japanese or Chinese language may produce sub-optimal output when a mixed Japanese- Chinese text is encountered)


6. Changes from RFC3066

The main goals were to maintain backward compatibility (so that all previous codes would remain valid); reduce the need for large numbers of registrations; to provide a more formal structure to allow parsing into subtags even where software does not have the latest registrations; to provide stability in the face of potential instability in ISO 639, 3166, and 15924 codes (demonstrated instability in the case of ISO 3166); and to allow for external extension mechanisms.

Substantive changes between draft-01 and this version are:

  • Added a reference to the most recent version of the UN country IDs to the address information in section 2.2.2.
  • Removed references to the 'i-klingon' tags (previously used as examples) since that tag is now deprecated (due to the addition of the ISO639-2 tag 'tlh').
  • Made the choice of UN or ISO3166 codes explicit in Section 2.2 and modified the text of Rule 7a. It also sets a start date for ambiguity resolution.
  • Prohibited future registration of "i-" prefixed tags or subtags.
  • Extensive non-substantive edits were made to the text to clarify positioning and make the rules for subtag assignment clearer.

  •  TOC 


    [1] International Organization for Standardization, "ISO 639-2:1998 - Codes for the representation of names of languages -- Part 2: Alpha-3 code - edition 1", August 1988.
    [2] ISO TC46/WG3 and M. Everson, Ed., "ISO 15924:2003 (E/F) - Codes for the representation of names of scripts", March 2003.
    [3] International Organization for Standardization, "Code for the representation of names of languages, 1st edition", ISO Standard 639, 1988.
    [4] International Organization for Standardization, "Codes for the representation of names of countries, 3rd edition", ISO Standard 3166, August 1988.
    [5] Statistical Division, United Nations, "Standard Country or Area Codes for Statistical Use", UN Standard Country or Area Codes for Statistical Use, Revision 4 (United Nations publication, Sales No. 98.XVII.9, June 1999.
    [6] Hardcastle-Kille, S., "Mapping between X.400(1988) / ISO 10021 and RFC 822", RFC 1327, May 1992.
    [7] Borenstein, N. and N. Freed, "MIME (Multipurpose Internet Mail Extensions) Part One: Mechanisms for Specifying and Describing the Format of Internet Message Bodies", RFC 1521, September 1993.
    [8] Alvestrand, H., "Tags for the Identification of Languages", RFC 1766, March 1995.
    [9] Hovey, R. and S. Bradner, "The Organizations Involved in the IETF Standards Process", BCP 11, RFC 2028, October 1996 (HTML, XML).
    [10] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997 (HTML, XML).
    [11] Crocker, D. and P. Overell, "Augmented BNF for Syntax Specifications: ABNF", RFC 2234, November 1997.
    [12] Berners-Lee, T., Fielding, R. and L. Masinter, "Uniform Resource Identifiers (URI): Generic Syntax", RFC 2396, August 1998 (HTML, XML).
    [13] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 2434, October 1998 (HTML, XML).
    [14] Fielding, R., Gettys, J., Mogul, J., Frystyk, H., Masinter, L., Leach, P. and T. Berners-Lee, "Hypertext Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999 (HTML, XML).
    [15] Carpenter, B., Baker, F. and M. Roberts, "Memorandum of Understanding Concerning the Technical Work of the Internet Assigned Numbers Authority", RFC 2860, June 2000.
    [16] Alvestrand, H., "Tags for the Identification of Languages", BCP 47, RFC 3066, January 2001.
    [17] Yergeau, F., "UTF-8, a transformation format of ISO 10646", STD 63, RFC 3629, November 2003.


    Authors' Addresses

      Addison Phillips (editor)
      webMethods, Inc.
      432 Lakeside Drive
      Sunnyvale, CA 94088
      Mark Davis


    Appendix A. Acknowledgements

    Any list of contributors is bound to be incomplete; please regard the following as only a selection from the group of people who have contributed to make this document what it is today.

    The contributors to RFC 3066 and RFC 1766, the precursors of this document, made enormous contributions directly or indirectly to this document and are generally responsible for the success of language tags.

    The following people (in alphabetical order) contributed to this document or to RFCs 1766 and 3066:

    Glenn Adams, Harald Tveit Alvestrand, Tim Berners-Lee, Marc Blanchet, Nathaniel Borenstein, Eric Brunner, Sean M. Burke, Jeremy Carroll, John Clews, Jim Conklin, Peter Constable, John Cowan, Mark Crispin, Dave Crocker, Martin Duerst, Michael Everson, Doug Ewell, Ned Freed, Tim Goodwin, Dirk-Willem van Gulik, Marion Gunn, Paul Hoffman, Richard Ishida, Olle Jarnefors, Kent Karlsson, John Klensin, Alain LaBonte, Eric Mader, Keith Moore, Chris Newman, Masataka Ohta, George Rhoten, Markus Scherer, Keld Jorn Simonsen, Thierry Sourbier, Otto Stolz, Tex Texin, Rhys Weatherley, Misha Wolf, Francois Yergeau and many, many others.

    Very special thanks must go to Harald Tveit Alvestrand, who originated RFCs 1766 and 3066, and without whom this document would not have been possible. Special thanks must go to Michael Everson, who has served as language tag reviewer for almost the complete period since the publication of RFC 1766.


    Appendix B. Examples of Language Tags (Informative)

    Simple language code:

    de (German)
    fr (French)
    ja (Japanese)

    Language code plus Script code :

    zh-Hant (Traditional Chinese)
    en-Latn (English written in Latin script)
    sr-Cyrl (Serbian written with Cyrillic script)


    zh-Hans-CN (Simplified Chinese for the PRC)
    sr-Latn-891 (Serbian, Latin script, Serbia and Montenegro)


    en-Latn-US-boont (Boontling dialect of English)


    de-DE (German for Germany)
    zh-SG (Chinese for Singapore)
    cs-CS (Czech for Czechoslovakia)
    sr-891 (Serbian for Serbia and Montenegro, UN country code, see 7a in Section 2.3

    Other Mixtures:

    zh-CN (Chinese for the PRC)
    en-boont (Boontling dialect of English)

    Extension mechanism:


    Extended language subtags:


    Private Use tags:

    qaa-Qaaa-QM-xsouthern (all private tags)
    de-Qaaa (German, with a private script)
    de-Latn-QM (German, Latin-script, private region)
    de-Qaaa-DE (German, private script, for Germany)

    Some Invalid Tags:

    de-891-DE (two region tags)
    a-DE (use of a single character tag)
    zh-xsouthern-DE (private use variant followed by another tag)


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