Last Updated: 2024-04-26

MIME stands for Multipurpose Internet Mail Extensions

It is an internet standard that extends the format of email messages to support text in character sets other than ASCII, as well attachments of audio, video, images, and application programs.

It is mostly transmitted with SMTP or IMAP etc. However its content types are now used in HTTP, where servers insert MIME header fields (Content-x) and clients use an appropriate viewer application based on the Content-Type field.

Details on Content-Type format

Example:

Content-Type: text/plain

Read the value as type (text) and subtype (plain)

multipart/mixed usually means a text/plain part and other non-text parts (e.g. attached file, with that file's original name in the Content-Disposition field)

Details on Content-Disposition field

Full example:

Content-Disposition: attachment; filename=genome.jpeg; modification-date="Wed, 12 Feb 1997 16:29:51 -0500";

• attachment means it is not displayed automatically and requires some user action first. Compare to inline - automatically display when message is read.

Criticisms

• The plain-text headers take up a lot of space and would be much smaller if sent with binary