Multipurpose Internet Mail Extensions (MIME) Part Two: Media Types
RFC 2046
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RFC - Draft Standard
(November 1996; Errata)
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2013-03-02
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RFC 2046 (Draft Standard)
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Network Working Group N. Freed
Request for Comments: 2046 Innosoft
Obsoletes: 1521, 1522, 1590 N. Borenstein
Category: Standards Track First Virtual
November 1996
Multipurpose Internet Mail Extensions
(MIME) Part Two:
Media Types
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.
Abstract
STD 11, RFC 822 defines a message representation protocol specifying
considerable detail about US-ASCII message headers, but which leaves
the message content, or message body, as flat US-ASCII text. This
set of documents, collectively called the Multipurpose Internet Mail
Extensions, or MIME, redefines the format of messages to allow for
(1) textual message bodies in character sets other than
US-ASCII,
(2) an extensible set of different formats for non-textual
message bodies,
(3) multi-part message bodies, and
(4) textual header information in character sets other than
US-ASCII.
These documents are based on earlier work documented in RFC 934, STD
11, and RFC 1049, but extends and revises them. Because RFC 822 said
so little about message bodies, these documents are largely
orthogonal to (rather than a revision of) RFC 822.
The initial document in this set, RFC 2045, specifies the various
headers used to describe the structure of MIME messages. This second
document defines the general structure of the MIME media typing
system and defines an initial set of media types. The third document,
RFC 2047, describes extensions to RFC 822 to allow non-US-ASCII text
Freed & Borenstein Standards Track [Page 1]
RFC 2046 Media Types November 1996
data in Internet mail header fields. The fourth document, RFC 2048,
specifies various IANA registration procedures for MIME-related
facilities. The fifth and final document, RFC 2049, describes MIME
conformance criteria as well as providing some illustrative examples
of MIME message formats, acknowledgements, and the bibliography.
These documents are revisions of RFCs 1521 and 1522, which themselves
were revisions of RFCs 1341 and 1342. An appendix in RFC 2049
describes differences and changes from previous versions.
Table of Contents
1. Introduction ......................................... 3
2. Definition of a Top-Level Media Type ................. 4
3. Overview Of The Initial Top-Level Media Types ........ 4
4. Discrete Media Type Values ........................... 6
4.1 Text Media Type ..................................... 6
4.1.1 Representation of Line Breaks ..................... 7
4.1.2 Charset Parameter ................................. 7
4.1.3 Plain Subtype ..................................... 11
4.1.4 Unrecognized Subtypes ............................. 11
4.2 Image Media Type .................................... 11
4.3 Audio Media Type .................................... 11
4.4 Video Media Type .................................... 12
4.5 Application Media Type .............................. 12
4.5.1 Octet-Stream Subtype .............................. 13
4.5.2 PostScript Subtype ................................ 14
4.5.3 Other Application Subtypes ........................ 17
5. Composite Media Type Values .......................... 17
5.1 Multipart Media Type ................................ 17
5.1.1 Common Syntax ..................................... 19
5.1.2 Handling Nested Messages and Multiparts ........... 24
5.1.3 Mixed Subtype ..................................... 24
5.1.4 Alternative Subtype ............................... 24
5.1.5 Digest Subtype .................................... 26
5.1.6 Parallel Subtype .................................. 27
5.1.7 Other Multipart Subtypes .......................... 28
5.2 Message Media Type .................................. 28
5.2.1 RFC822 Subtype .................................... 28
5.2.2 Partial Subtype ................................... 29
5.2.2.1 Message Fragmentation and Reassembly ............ 30
5.2.2.2 Fragmentation and Reassembly Example ............ 31
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