MIME

MIME is an Internet Standard for Multipurpose Internet Mail Extensions,

MIME was developed to provide a way of embedding binary content in E-mail. Traditional E-mail is only guaranteed to support the 7-bit ASCII character set, so a way was needed to encode 8-bit binary content such as programs, images, sounds, and movies in a form that could be carried in a 7-bit E-mail message.

MIME was designed so that different character encoding schemes could be developed, and also provided a simple sort of metadata in the form of MIME types[?], so that applications could work out what kind of content was contained in the E-mail message, and therefore know what kind of processing was needed to use the content.

A MIME multipart message contains a boundary in the Content-type: header; this boundary, which must not occur in any of the parts, is placed between the parts, and at the beginning and end of the body of the message, as follows:

Content-type: multipart/mixed; boundary="frontier"
MIME-version: 1.0

--frontier
Content-type: text/plain

This is the body of the message.
--frontier
Content-type: application/octet-stream
Content-transfer-encoding: base64

gajwO4+n2Fy4FV3V7zD9awd7uG8/TITP/vIocxXnnf/5mjgQjcipBUL1b3uyLwAVtBLOP4nV
LdIAhSzlZnyLAF8na0n7g6OSeej7aqIl3NIXCfxDsPsY6NQjSvV77j4hWEjlF/aglS6ghfju
FgRr+OX8QZMI1OmR4rUJUS7xgoknalqj3HJvaOpeb3CFlNI9VGZYz6H6zuQBOWZzNB8glwpC
--frontier--

Although HTTP does not use MIME encoding, it re-used the concept of MIME types to encode the types of binary content.

References:

• RFC 2045 - Full text of RFC 2045 (http://www.ietf.org/rfc/rfc2045.txt) Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies. N. Freed, N. Borenstein. November 1996. (Format: TXT=72932 bytes) (Obsoletes RFC 1521, RFC 1522[?], RFC 1590) (Updated by RFC 2184, RFC 2231) (Status: DRAFT STANDARD)
• RFC 2046 - Full text of RFC 2046 (http://www.ietf.org/rfc/rfc2046.txt) Multipurpose Internet Mail Extensions (MIME) Part Two: Media Types. N. Freed, N. Borenstein. November 1996. (Format: TXT=105854 bytes) (Obsoletes RFC 1521, RFC 1522[?], RFC 1590) (Updated by RFC 2646) (Status: DRAFT STANDARD)
• RFC 2047 - Full text of RFC 2047 (http://www.ietf.org/rfc/rfc2047.txt) MIME (Multipurpose Internet Mail Extensions) Part Three: Message Header Extensions for Non-ASCII Text. K. Moore. November 1996. (Format: TXT=33262 bytes) (Obsoletes RFC 1521, RFC 1522[?], RFC 1590) (Updated by RFC 2184, RFC 2231) (Status: DRAFT STANDARD)
• RFC 2048 - Full text of RFC 2048 (http://www.ietf.org/rfc/rfc2048.txt) Multipurpose Internet Mail Extensions (MIME) Part Four: Registration Procedures. N. Freed, J. Klensin, Jon Postel. November 1996. (Format: TXT=45033 bytes) (Obsoletes RFC 1521, RFC 1522[?], RFC 1590) (Updated by RFC 3023) (Also BCP0013) (Status: BEST CURRENT PRACTICE)
• RFC 2049 - Full text of RFC 2049 (http://www.ietf.org/rfc/rfc2049.txt) Multipurpose Internet Mail Extensions (MIME) Part Five: Conformance Criteria and Examples. N. Freed, N. Borenstein. November 1996. (Format: TXT=51207 bytes) (Obsoletes RFC 1521, RFC 1522[?], RFC 1590) (Status: DRAFT STANDARD)

External link:

• List of MIME Media Types (http://www.iana.org/assignments/media-types/)