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4.5. 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

application/postscript PostScript viewer A
.aif, .aiff audio/x-aiff AIFF file B
.aifc audio/aifc Compressed AIFF file B
.au audio/basic -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

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