Mime Types

To give the client a hint of what to do with a file, the HTTP protocol defines that each file should be sent with a Mime type. A Mime type consists of a Content type and a subtype. The Content type is one of application, audio, example, image, message, model, multipart, text, and video. Subtypes can be registered with IANA by a Web form. The Internet Assigned Numbers Authority (IANA) maintains a list of mime types. Most Linux or BSD systems have a local list at /etc/mime.types. The authoritative list can be found at http://www.iana.org/assignments/media-types.

For a single web project, a fairly small map of mime types will usually suffice:

mimetype.assign = (
".html" => "text/html",
".txt" => "text/plain",
".jpg" => "image/jpeg",
".jpeg" => "image/jpeg",
".gif" => "image/gif",
".png" => "image/png",
".zip" => "application/zip",
".tar.gz" => "application/x-tgz",
".gz" => "application/x-gzip")

Note the last two entries; the order is of the essence here. Had we swapped them, any .tar.gz file would match .gz and would thus be served as application/x-gzip.

The standard mime type for an HTML page is "text/html", but this changes if you use XHTML, which can be sent as "text/html", "text/xml" or "application/xml", the correct type being "application/xhtml+xml". Some browsers react differently on each type. Storing them with the extension " .xhtml" will make it easier to distinguish between HTML and XHTML files.

If the file system in use supports XFS-style attributes, we can set the mime type for each file with the attr program:

attr -s Content-Type -V image/jpeg foto.jpg

This Content-Type attribute can be used wherever it is present by setting

mimetype.use-xattr = "enable"

in our lighttpd.conf file, Lighttpd will fall back to the mime-type.assignment for files without Content-Type attribute.