Webmaster Tip

File Formats & Extensions

All information stored in your computer, or on your Website must be in a file. A file is a collection of data or information. Every file has a file name and a file extension.

A file extension identifies the file type. For example:

• Text files have extensions such as .txt, .html, etc.
• Formatted files have extensions such as .doc, .pdf, etc.
• Compressed files have extensions such as .sit, zip, etc.
• Image files have extensions such as .gif, .jpg/jpeg, etc.
• Sound files have extensions such as .wav, .mid, etc.
• Video files have extensions such as .avi, .mov/.movie, etc.

Depending on your operating system (Windows, Mac, or UNIX) each of the file extensions may require special software to view, create, and manipulate.

A partial listing of the most common Internet files used today, their file extension and software needed to view, create, or manipulate these files is shown below:

Text Files
.css - a file with this extension contains a link to an external cascading style sheet. Cascading Style Sheets, is a new feature being added to HTML that gives Website developers more control over how pages are displayed. To view a .css file, use Notepad for the PC. For the Mac use Simple Text.

.html - a file with this extension is a HyperText Markup Language file. HTML is the standard mark up language used to create Web pages. This mark up language tells a Web browser how to display a Web page and requires a browser, such as Navigator or Internet Explorer, to view.

.txt - a file with this extension is a plain text file. This file can be created or viewed with Notepad or a word processor like Microsoft Word. For the Mac you can use Simple Text or BBEdit.

Formatted Documents
.doc - a file with this extension is word processing documents. Usually these are documents created using Microsoft Word or WordPerfect for Windows and can be viewed with Microsoft Word or WordPerfect for Windows.

.pdf - a file with this extension is using the Portable Document Format. A .pdf file is a proprietary format developed by Adobe Systems, Inc. It enables documents (including brochures or other documents containing artwork) to be transferred over the Internet, so they look the same on any computer. To view you need an Adobe Acrobat Reader.

.ps - a file with this extension is PostScript file. This is technically a plain text file, but is unreadable unless you have a Postscript printer or use a screen viewer like Ghostscript. Ghostscript is available for Mac, Windows, and UNIX.

Compressed Files
.arj - a file with this extension is a compressed file. To uncompress these file for Windows, you can use Stuffit Expander for Windows or WinZIP. For the Mac you can use UnArjMac.

.exe - a file with this extension is either a DOS or Windows program or a self-extracting file.
If this is an executable (self-extracting) file, then it can usually be started by double-clicking the icon. This is the only way to tell if it is an executable file.

.sit - a file with this extension is a Macintosh file that has been compressed using a program called Stuffit.
To unstuff a file with a .SIT extension, you need a program called Stuffit Deluxe or you can use Stuffit Expander for the Mac or for Windows.

.sea - a file with this extension is a Macintosh self-extracting archive file. An archive file is usually a collection of files that have been combined into one to make it easy to download. Because the archive is self-extracting, you don't need any special application or utility to launch it. You simply click on the icon from the Macintosh desktop and it decompresses and un-bundles the files.

.Z - a file with this extension is a UNIX compressed file. You can use WinZIP to decompress and view a file with this extension, or try Stuffit Expander for the Mac.

.zip - a file with this extension is a common compression standard for DOS and Windows. These files can be decompressed for the PC with WinZIP. You can also use Stuffit Expander for Mac or Windows.

Graphics Files
.gif - a file with this extension is the most common graphics file format used on the Internet. GIF stands for Graphics Interchange Format. If your browser does not have a built-in GIF viewer (most do), try Lview Pro or PolyVie to view these graphics for a Windows PC. For the Mac, you can use a shareware utility called GIF Converter to view and modify GIFs.

.jpg/jpeg - a file with this extension is another popular compression standard used for photos. You can view JPEG files with most web browsers as long as you have a JPEG viewer. For the Mac, you can use JPEGView.

All of the above graphics formats can also be viewed, created, or manipulated with one or more commercially available graphics software programs like Photostyler or PhotoShop for Windows. For the Mac you can use PhotoShop or DeBabelizer.

Sound Files
.au - a file with this extension is one of the most common sound format found on the Web.
Macs need Sound App to play this type of file; PCs can use Waveform Hold and Modify (whamxxx.zip) which provides support for a variety of formats, conversion between them, and file editing functions.

.aiff - a file with this extension is another common sound file. It is short for Audio Interchange File Format. The format was developed by Apple Computer and is the standard audio format for Mac computers. But, it can be used on your PC as well. It requires the same programs as .au to play.

.mp3 - a file with this extension is the most popular file format on the Web used to distribute CD-quality music. It requires a MP3 player. which is available for both Windows and the Mac. Note: a 1 Mb file is equal to about one minute of music.

.ra - a file with this extension is streaming audio file. It was developed by RealNetworks, RealAudio allows you to play sound files in real-time. This type of file requires the RealPlayer, available for both Macintosh and Windows.

.wav - a file with this extension is the native sound format for Windows. For the Mac, you can use Sound App to play .wav files.

Video Files
.avi - a file with this extension is the standard video format used for Windows. These files need an AVI Video for Windows player or the Windows Media Player from Microsoft.

.mov/.movie - a file with this extension is the common format for QuickTime movies, the Macintosh native movie platform. You can use a number of applications to play .mov files including Sparkle or MoviePlayer on the Mac, and QuickTime for Windows.

.mpg/mpeg - a file with this extension is standard format for "movies" on the Internet, using the MPEG compression scheme. On the Mac, use Sparkle to play ,mpg files or to convert them to QuickTime movies. There are a variety of MPEG Players for Windows and an MPEG FTP Site that has a large collection of MPEG player resources for all platforms (Mac, Windows, and UNIX).

.qt - a file with this extension is another extension that denotes a QuickTime movie. Use the latest version of Quicktime for the Mac.

.ram - a file with this extension is a popular format from RealNetworks for streaming video. To view these files, you need the RealPlayer, which can be downloaded from Real.com.

For additional file information.

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