Apache: The Definitive Guide, 3rd Edition

MIME Types

MIME stands for Multipurpose Internet Mail Extensions, a standard developed by the Internet Engineering Task Force for email but then repurposed for the Web. Apache uses mod_mime.c, compiled in by default, to determine the type of a file from its extension. MIME types are more sophisticated than file extensions, providing a category (like “text,” “image,” or “application”), as well as a more specific identifier within that category. In addition to specifying the type of the file, MIME permits the specification of additional information, like the encoding used to represent characters.

The “type” of a file that is sent is indicated by a header near the beginning of the data. For instance:

content-type: text/html

indicates that what follows is to be treated as HTML, though it may also be treated as text. If the type were “image/jpg”, the browser would need to use a completely different bit of code to render the data.

This header is inserted automatically by Apache^[1] based on the MIME type and is absorbed by the browser so you do not see it if you right-click in a browser window and select “View Source” (MSIE) or similar. Notwithstanding, it is an essential element of a web page.

The list of MIME types that Apache already knows about is distributed in the file ..conf/mime.types or can be found at http://www.isi.edu/in-notes/iana/assignments/media-types/media-types. You can edit it to include extra types, or you can use the directives discussed in this chapter. The default ...