rfc-3282

Content Language Headers

H. Alvestrand

date2002-05 streamIETF wgnon working group statusDRAFT STANDARD pages8 canonicalhttps://www.rfc-editor.org/rfc/rfc3282 doi10.17487/RFC3282

This document defines a "Content-language:" header, for use in cases where one desires to indicate the language of something that has RFC 822-like headers, like MIME body parts or Web documents, and an "Accept-Language:" header for use in cases where one wishes to indicate one's preferences with regard to language. [STANDARDS-TRACK]

obsoletes

rfc-1766 — Tags for the Identification of Languages

Extracted elements (10)

design-rationale §Appendix A

The 'differences' parameter to multipart/alternative that was defined in RFC 1766 has been removed from this specification because no implementations of that function were ever found.

interoperability-note §3

If no Q values are present in Accept-Language, language-ranges are treated as ordered by priority with the leftmost being most preferred. This is an extension to HTTP/1.1 rules but matches existing practice. When Q values are present, HTTP/1.1 (RFC 2616) evaluation rules apply.

http

interoperability-note §2

Language tag syntax and semantics (language-range, language-tag values) are defined externally in BCP 47 / RFC 3066 and ISO 639; this document only specifies the header syntax for carrying those tags in RFC 822-style headers.

http, email

normative-requirement §3 MUST

Conforming implementations MUST accept the obs-accept-language syntax but MUST NOT generate it; all generated Accept-Language headers MUST conform to the strict Accept-Language ABNF.

http, email

normative-requirement §2 MUST

Conforming implementations MUST accept the obs-content-language syntax (which permits optional whitespace before the colon) but MUST NOT generate it; all generated Content-Language headers MUST conform to the strict Content-Language ABNF.

http, email

protocol-element §3

The Accept-Language header expresses a user's or process's preferred language(s) for RFC 822-like content. It lists one or more language-ranges, each optionally qualified with a quality value Q as defined in HTTP/1.1.

http, email

protocol-element §2

The Content-Language header indicates the language(s) of RFC 822-like content such as MIME body parts or Web documents. It carries one or more language tags as defined in BCP 47 (RFC 3066), separated by commas.

http, email

security-consideration §4

Language ranges used in content negotiation may allow a recipient to infer the sender's nationality, creating a potential surveillance target. The exact threat magnitude and countermeasures are delegated to each application protocol.

privacy, security

wire-format §3

Accept-Language ABNF: `Accept-Language = "Accept-Language:" [CFWS] language-q *(",[CFWS] language-q)` where `language-q = language-range [";" [CFWS] "q=" qvalue] [CFWS]` and qvalue is a decimal in [0,1] with up to three fractional digits.

http, email

wire-format §2

Content-Language ABNF: `Content-Language = "Content-Language" ":" [CFWS] Language-List` where `Language-List = Language-Tag [CFWS] *(",[CFWS] Language-Tag [CFWS])`. Multiple language tags are comma-separated; CFWS permits whitespace and parenthesized comments.

http, email