Glossary of Computer File Extensions

Filename Extensions List

So you see a file somewhere on the 'net with a name like "" 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 .

f3 & f3b
The Sun Folio format is used for storing vector fonts. It originated on Sun UNIX systems but will work on many X-Windows systems.
f66, f77, & f90
A source file written in the ForTran programming language. It should be in simple ASCII and (depending upon how portably it was written) should be usable on any machine with a ForTran compiler. The only caution is that the number refers to the version of ForTran used.
A FAQ file is traditionally a simple ASCII document that attempts to answer frequently asked questions.
A format exported by an organizational software application called Topicscape. It is in simple ASCII and can thus be viewed on pretty much any machine, although it can only be usefully imported into Topicscape.
A Macromedia Flash source document. Can be used with any machine that has the commercial Macromedia Flash editor, currently available for only Macintosh and MS-Windows.
This indicates a FrameMaker native format document. Such a file may only be read with FrameMaker or FrameViewer or similar (currently only available for a price on UNIX, Mac, & WinTel platforms).
This file is a Frogans Network Certificate. It is a small file used to permit the initialization of a Frogans network.
The FlashPix image format was developed by Kodak but is now governed by an independent organization called the Digital Imaging Group. Programs for viewing this format are available for a few different platforms. An extended version of this format can also handle audio, but this variant is not too widely supported at this time.
The IBM Triton FastTrack format is an audio format. It is not too widely recognized.