Appendix B

Commonly Used MIME Media Types

by Michael Ellsworth

Several types and subtypes of Multipurpose Internet Mail Extensions (MIME) were defined by Request For Comments (RFC) 1341 in 1992. Many more have subsequently been approved by the Internet Assigned Numbers Authority (IANA). It was the expressed intention of the original RFC that the number of MIME types be limited to the seven proposed in the RFC, as follows:

• Application. A catch-all description allowing for miscellaneous file types.
• Audio. Used for audio such as Sun u-law (au) or Microsoft Windows WAV files.
• Image. Used for graphics files, such as GIF or JPEG.
• Message. Used for various types of messages, including messages that refer to other messages for elements of their bodies.
• Multipart. Indicates that it contains multiple sections with potentially more than one MIME type.
• Text. Used to describe text of various types, including plain text (e-mail) and HTML, although HTML isn't an approved subtype.
• Video. Used for video files such as QuickTime or Microsoft Video files.

Within each type, various subtypes are allowed and are appended to the type with a slash (/). Tables B.1 through B.7 list all the IANA-approved MIME types and subtypes (in boldface italic) as well as additional types that appear to be supported by the popular servers and browsers. In addition to the types indicated, NCSA Mosaic 2.0 supports a type of telnet (with no subtype). I'm indebted to Ken Jenks for his list found at http://sd-www.jsc.nasa.gov/mime-types/.

To find out about current IANA-approved media types, visit the anonymous FTP site ftp://ftp.isi.edu/in-notes/iana/assignments/media-types/.