Metadata Resources

Multipurpose Internet Mail Extensions - MIME

MIME - the Multipurpose Internet Mail Extensions - [RFC-2045] defines a format that allows Internet email [RFC-822] to carry multipart textual and non-textual messages without loss of data. Each message part is assigned a 'Content-Type' header that allows MIME processing software to determine the format of data that is contained in that part. A Content-Type is made up of two parts; a general 'type', for example 'text', and a more specific 'sub-type', for example 'html'. Such a Content-Type is represented in the form 'text/html'. To allow for multipart messages there is a special type of 'multipart'. Associated with the 'multipart' type are several sub-types including 'alternative' and 'mixed'. Where binary data is being transfered, the body part is assigned a 'Content-Transfer-Encoding' header which allows the data to be encoded as plain text for transmission using email. Finally, MIME supports the use of multiple character sets for the 'text' Content-Types using the 'charset' parameter.

MIME Content-Types are registered with IANA.

Although MIME was originally developed to enhance mail functionality it is also used by other transport mechanisms including HTTP [RFC-1945]. The most important difference between MIME as used in mail [RFC-1521] and MIME as used in HTTP is that no use needs to be made of the Content-Transfer-Encoding header because binary data can be carried directly without encoding.


MIME resources

Maintained by: Andy Powell
Last updated: 20-Apr-2000

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