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Tags for the Identification of Languages (RFC1766) Disclosure Number: IPCOM000004017D
Original Publication Date: 1995-Mar-01
Included in the Prior Art Database: 2019-Feb-12
Document File: 9 page(s) / 12K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

H. Alvestrand: AUTHOR

Related Documents

10.17487/RFC1766: DOI


This document describes a language tag for use in cases where it is desired to indicate the language used in an information object. [STANDARDS-TRACK]

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This is the abbreviated version, containing approximately 21% of the total text.

Network Working Group H. Alvestrand Request for Comments: 1766 UNINETT Category: Standards Track March 1995

Tags for the Identification of Languages

Status of this Memo

This document specifies an Internet standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "Internet Official Protocol Standards" (STD 1) for the standardization state and status of this protocol. Distribution of this memo is unlimited.


This document describes a language tag for use in cases where it is desired to indicate the language used in an information object.

It also defines a Content-language: header, for use in the case where one desires to indicate the language of something that has RFC-822- like headers, like MIME body parts or Web documents, and a new parameter to the Multipart/Alternative type, to aid in the usage of the Content-Language: header.

1. Introduction

There are a number of languages spoken by human beings in this world.

A great number of these people would prefer to have information presented in a language that they understand.

In some contexts, it is possible to have information in more than one language, or it might be possible to provide tools for assisting in the understanding of a language (like dictionaries).

A prerequisite for any such function is a means of labelling the information content with an identifier for the language in which is is written.

In the tradition of solving only problems that we think we understand, this document specifies an identifier mechanism, and one possible use for it.

Alvestrand [Page 1]

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 whic...