Web Design in a Nutshell

File (MIME) Types

Servers add a header to each document that tells the browser the type of file it is sending. The browser determines how to handle the file based on that information—whether to display the contents in the window, or to launch the appropriate plug-in or helper application.

The system for communicating media types closely resembles MIME (Multipurpose Internet Mail Extension), which was originally developed for sending attachments in email. The server needs to be configured to recognize each MIME type in order to successfully communicate the media type to the browser.

If you want to deliver media beyond the standard HTML files and graphics (such as a Shockwave Flash movie or an audio file), you should contact your server administrator to be sure the server is configured to support that MIME type. Most common formats are built in to current versions of server software, but if it isn’t there already, the administrator can easily set it up if you provide the necessary information.

The exact syntax for configuring MIME types varies among server software; however, they all require the same basic information: type, subtype, and extension. Types are the most broad categories for files. They include text, image, audio, video, application, etc. Within each category are a number of subtypes. For instance, the file type image includes the subtypes gif, jpeg, etc. The extension refers to the file’s suffix, which the server uses to determine the file type and subtype. Not all extensions are standardized.

Table 4.3 lists common media types by extension along with their MIME type/subtype information. The ASCII/Binary information is provided to aid in making upload decisions.

Of course, new technologies and file types are emerging every day, so keep in mind that it is the web designer’s responsibility to make sure that for any new media type the appropriate information is communicated to the server administrator.

Table 4-3. MIME Types and Subtypes by Extension

Extension	Type/Subtype	Description	ASCII/Binary
.ai	application/postscript	PostScript viewer	A
.aif, .aiff	audio/x-aiff	AIFF file	B
.aifc	audio/aifc	Compressed AIFF file	B
.au	audio/basic	μ-law sound file	B
.avi	video/avi or video/x-msvideo	AVI video file	B
.bmp	image/x-MS-bmp	Microsoft BMP file	B
.dcr, .dir, .dxr	x-director	Shockwave files	B
.doc	application/msword	Microsoft Word document	B
.eps	application/postscript	Encapsulated PostScript	A
.exe	x-msdownload	Self-extracting file or executable	B
.gif	image/gif	Graphic in GIF format	B
.gz	x-gzip	Compressed file, use gunzip (Unix decompressor)	B
.hqx	mac-binhex40	Mac BinHex Archive	B
.htm	text/html	HTML document	A
,jpg,.jpeg, .jpe, .jfif, .pjpeg, .pjp	image/jpeg	Graphic in JPEG format	B
.mid	audio/midi or audio/x-midi	MIDI audio file	B
.mov	video/quicktime	QuickTime movie	B
.movie	video/x-sgi-movie	Silicon Graphics movie	B
.mp2, .mp3, .mpa	video/mpeg	MPEG movie	B
.pbm	image/x-portable-bitmap	Portable bitmap image	B
.pcd	image/x-photo-cd	Kodak photo CD image	B
.pdf	application/pdf	Portable Document Format (Acrobat file)	B
.pic	image/x-pict	PICT image file	B
.pl	x-perl	Perl source file	A
.png	image/x-png	Graphic in PNG format	B
.ppt	application/powerpoint	PowerPoint file	B
.ps	application/postscript	PostScript file	A
.qt	video/quicktime	QuickTime movie	B
.ra, .ram	audio/x-pn-realaudio	RealAudio file (and metafile)	B
.rtx	text/richtext	Rich Text Format (Microsoft Word)	A
.rtf	application/rtf	Rich Text Format (MSWord)	A
.sea	x-sea	Self-extracting Archive (Stuffit file)	B
.sit	x-sit	Stuffit Archive	B
.snd	audio/basic	Digitized sound file	B
.swf	application/x-shockwave-flash	Shockwave Flash file	B
.tar	x-tar	Compressed file	B
.tif, .tiff	image/tiff	TIFF image (requires external viewer)	B
.txt	text/plain	ASCII text file	A
.wav	audio/s-wav	Waveform audio file	B
.wrl, .wrz	x-world/x-vrml	VRML 3D file (requires VRML viewer)	B
.xll	vnd.ms-excel	Microsoft Excel File	B
.zip	x-zip-compressed	Compressed file (decompress using WinZip or Stuffit on Mac)	B