MIME TYPES

This subsection describes MIME types and why they are important.

MIME is an acronym for Mulitpurpose Internet Mail Extensions. As RFC 1521, it represents a standard for describing data types. It is information about data. As originally concieved, it was designed as an extention to the Simple Mail Transfer Protocol (RFC 822) allowing people to send binary data (like pictures and sounds) as enclosures with email messages.

The standard was flexible enough that it could be easily incorporated into HTTP. Consequently, MIME provides the mechanism for seemlessly tranfering non-text data easily to your browser. (Incidentally, the gopher protocol did not support MIME. If it had, then maybe it would have proved a more valuable tool.)

A particular MIME type is a pair of elements delimited by a slash ("/"). The first element describes the "type" of data. Examples include but are not limited to:

• application
• audio
• image
• text
• video

• msword
• gif
• jpeg
• mpeg
• quicktime
• html
• plain

Complete MIME types then include some of the following examples. You have probably seen these sorts of things while configuring your WWW browser for helper applications:

• application/msword
• application/macwriteii
• application/postscript
• application/zip
• application/x-tar
• audio/basic
• audio/x-wav
• text/html
• text/plain
• image/gif
• image/jpeg
• video/mpeg
• video/quicktime

Thus, when your browser (or email application) recieves a MIME type of application/msword it is expected to know what application to run (Microsoft Word) and handle it accordingly. Simiarly, when your browser recieved some data of type text/html (the most common WWW MIME type), then your browser knows to interpret the incomming data as HTML and display it.

As a WWW server administrator, MIME types are important because you have to know what kinds of data you are serving to your constituents. These kinds of data are described with MIME. All WWW server applications come configured to handle most MIME types, but when a new data type becomes available, you will have to know a bit about MIME in order for you to server it correctly.