An Internet media type is, generally speaking, a property of a data set, describing both the general type of data (such as "text" or "image" or "application"; the last one refers to program-specific internal data formats) and, as a subtype, a specific format for the data. The concept was originally defined as "MIME content types".
Media types relate to HTML as follows:
- When a Web server sends an HTML document, it should
specify the correct media type (
text/html) in the HTTP headers it sends along with the document. Normally servers are configured to do this by default when the file name ends with
.htm(depending on the system; please consult local documentation).
- In a FORM element, the value of the ENCTYPE attribute specifies the media type to be used then encoding and sending the content of the form.
- When referring to various resources, such as embedding images
using IMG elements or linking to binary files
using an A element, there is no way to
tell the media type in HTML. Things must be handled in the server.
Typically, a Web server uses some mapping table to map
file name extensions to media types (eg mapping extension
.zipto media type
application/zip), and it may provide users some tools for overriding such mappings or otherwise specifying the media type to be associated with a file or set of files. The description of the A element contains some additional notes related to audio and video and binary files in general.
HTML 3.2 Reference Specification
refers to RFC 1521
but that specification was superseded by
(in November 1996).
The procedure for registering types in given in
it, the registry is kept at
You can check what is the media type information sent by a server
Assuming we are interested in the media type of the document at
a Telnet connection to host
using the port number in the URL if present, port 80 otherwise.
Then give the command
and then an empty line. Example (where the Telnet connection is established by starting the
telnet program from Unix command level):
beta ~ 51 % telnet www.hut.fi 80 Trying 126.96.36.199... Connected to info-e.hut.fi. Escape character is '^]'. HEAD /home/jkorpela/perhe.jpg HTTP/1.0 HTTP/1.1 200 OK Date: Tue, 23 Sep 1997 12:37:05 GMT Server: Apache/1.2.4 Last-Modified: Tue, 08 Aug 1995 08:29:53 GMT ETag: "16391-9232-30272081" Content-Length: 37426 Accept-Ranges: bytes Connection: close Content-Type: image/jpeg Connection closed by foreign host. beta ~ 52 % exitHere the
Content-Type:field tells that the media type is