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Web Design Reference Guide

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MIME Types

Last updated Oct 17, 2003.

If you manage a Web server or have a Web site, knowing which Multipurpose Internet Mail Extensions (MIME) Types (also referred to as MIME Media Types) are available from a server ensures it's safe to put such content on the Web page. The Internet Assigned Numbers Authority (IANA) manages the list of registered MIME Types. A MIME Type has two parts: The top-level type, which identifies the type of media; and the sub-type, which indicates the specific format of the media.

MIME Types work similarly to Windows Explorer's File Types. When installing a new application like Photoshop, its extension (PSD) is registered in Windows' registry so that when you click on a file with the .psd extension, Windows knows to open Photoshop to view the media.

MIME Types do the same thing, except instead of for Microsoft Windows, it does it over the Internet so browsers know what the non-ASCII message contains. When a file type appears in a browser, the MIME Type identifies the file type and enables the browser to display or output the file when it's something other than HTML. If it's a file type that isn't defined, then the user receives an error message in the browser. The following are MIME Types:

  • Application
  • Audio
  • Image
  • Text
  • Video

JPEG is a subtype of the image type. .jpg and .jpeg files are the extensions associated with these images. The media type of image/jpeg tells the browser an image is coming and it's formatted as a .jpeg. PNG and GIF are also image subtypes. If these MIME Media Types aren't set up in the server application, such as Apache or IIS, the client receives an error.