Telling the type: A server's job

The server, which is under control of the document provider, should know what kinds of documents it is serving.


Until recently, most of the files available on the Internet with the extension .doc were formated ASCII text files (content type text/plain). It's only been in the past few years that the alternative of that they are more commonly type application/x-msword.

It is up to the document provider system (the web server) to tell the client (the web browser) what the type is. A server could be configured to say text/plain for each .doc file. It could be configured to say application/x-msword for files it finds in particular directories. It could even be configured to give a specific content-type for a specific file.

Note that the server does not communicate to the client the general scheme it uses. It just provides content-type information for every file it serves.

MIME types

The general system for doing this is based on something called "MIME types." Things that provide documents often have a mime.types configuration file which generally maps file name extensions onto the content-types.

MIME was originally developed for Email, but it was also developed to be a general way of communicating this sort of information between document providers and others. The WWW wouldn't work without it.

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Jeff Goldberg