Multipurpose Internet Mail Extensions (MIME)

A short text string, e.g.:
text/plain text/html image/gif image/jpg video/mpeg application/msword application/excel
Delivered by server to client
Included in the message header as Content-Type:.
Enables the client to invoke the appropriate application for an attached data file (e.g. a spreadsheet, a word processor, a sound player)

Why "Mail"?

Originally devised for sending attachments with e-mail.
Serves the same purpose in the browser
In the context of the web, applications are termed helpers, viewers, or plug-ins.

Lab
The user can choose which application is invoked for a particular MIME type. Find out how, in Netscape, you choose applications. Internet Explorer uses a different mechanism. What is it?

How does the server know which MIME type to send to the browser?
That is, how does it choose the text string for the Content-Type header field?
- This is the only required HTTP header field
It looks up the filename extension in conf/mime.types

Lab
Look at `conf/mime.types`

Why not let the server simply tell the browser what app to run on the data?
What would happen in the browser if the server told it the wrong MIME type?
What does the server do if the filename extension of the desired file is not defined in mime.types?

Lab

Lab
Download `funny.xxx` by clicking on the hyperlink. See your browser misinterpret it. Place this file in your document root. Create a hyperlink that points to this file in a web page in your document root. What kind of interpretation is your browser assuming for `funny.xxx`? Add `xxx` to this line to your `mime.types` file: `application/msword doc` so that it becomes: `application/msword doc xxx` Restart Apache. Flush your browser's cache. Open the web page you just edited, click on the new link, and see what your browser does. What is the `Content-Type` this time?

Download funny.xxx by clicking on the hyperlink.
- See your browser misinterpret it.
Place this file in your document root.
Create a hyperlink that points to this file in a web page in your document root.
What kind of interpretation is your browser assuming for funny.xxx?
Add xxx to this line to your mime.types file:
application/msword doc
so that it becomes:
application/msword doc xxx
Restart Apache.
Flush your browser's cache.
Open the web page you just edited, click on the new link, and see what your browser does.
What is the Content-Type this time?

The other way to define a MIME type for a filename extension is with the AddTpe directive in srm.conf
How would you define the .xxx filename extension in srm.conf instead of in mime.types?
Solution