Saugus.net: Glossary of Computer File Extensions

Filename Extensions List

So you see a file somewhere on the 'net with a name like "greatfile.xyz" and you would like to download it and use it on your computer. Will it work? What does the file extension xyz mean, anyway? This handy guide attempts to provide answers to those questions.

It is not meant to be read straight through; rather, it is meant to be a reference. An extension may be looked up either with the "find in page" option of your browser or by appending a "#xyz" (without the quotes and with xyz replaced by the extension in question) to the "go to" or "URL" field on your browser. There is also a Search Interface that will return not only the specific extension sought but also other entries that reference it. Be aware though that it assumes familiarity with the computer basics discussed on the terms page.

You may notice that most extensions are three letters (or fewer) long. This is due to a historical limitation of the operating system called CP/M (that was later inherited by MS-DOS). In fact, the whole concept of file extensions comes from CP/M. Most modern operating systems do not attribute any special meaning to the "." (period, or dot) character.

Be aware though that there is no standardization to filename extension usage, and many different people have used extensions to apply to many different things. This list only attempts to provide likely guesses of what something is apt to be. Programs that can make use of many of these extensions can be found on the Guide to Free Software.

If you want something added or see a problem with something already here (but keep in mind this guide is not meant to be overly technical) please send .

wav: The waveform audio file format was originally developed on WinTel boxes but can now be played on many platforms. It is one of the most popular audio formats found on the web. It cannot be played on as many different machines as mono au files, though, so for simple voice recording the au format may be preferable.
wdb: A DataViz document; can be read on any machine with DataViz (MS Works) installed (available only for WinTel boxes and Macs, but usually not for free).
wdgt: Unfortunately this extension can mean one of two slightly incompatible things: an Apple Dashboard Widget or an Opera Widget. In each case it'll function a lot like an applet desktop accessory. In the former case it will work on computers running Mac OS X or KDE. In the latter case it will work on computers running the Opera browser. The Apple Widget will consist of a group of files kept together in an application bundle; the Opera Widget will consist of a group of files zipped together. See also the similar widget extension.
widget: This is probably a Yahoo! (formerly Konfabulator) Widget. It'll function a lot like an applet desktop accessory. It usually consists of a group of files zipped together. See also the similar wdgt extension.
wk1: A Lotus 123-2 document; can be read on any machine with Lotus 123 installed (available only for WinTel boxes, Macs, and some UNIX boxes, but usually not for free).
wks: A Lotus 123-1A document; can be read on any machine with Lotus 123 installed (available only for WinTel boxes, Macs, and some UNIX boxes, but usually not for free).
wmf: A Windows metafile is like an ordinary CGM metafile but possibly containing structures that make it specific to MS-Windows. It is not really more capable than the ordinary CGM format, but less portable and therefore less desirable.
wp, wp4, wp5, wp6, & wpd, wpp: A WordPerfect document. It is binary but will work directly on any machine that has WordPerfect.
wps: A Microsoft Works word processing document. It is binary and generally requires Microsoft Works to be read, although some versions of Microsoft Word will read some versions of Microsoft Works documents some of the time.
wra & wr3: A Wraptor file is similar in all respects to an arc file, but a different method of compression was used. Programs to uncompress this type of file are apparently only found on the C64/128.