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 .

An Apple Keynote document. It is a compound document built from XML files (and various types of media files) and will work on any machine that has Apple Keynote installed.
Usually a Koala Paint file; an image format originally designed for the Commodore 64, but readable by many other machines as well with the appropriate software.
This is most likely part of a Yahoo! (formerly Konfabulator) Widget. It will be simple ASCII typically containing a mix of XML and JavaScript.
A Komodo Project File contains XML data that defines a project for use with the Komodo software development tools.
Probably a Korn Shell script. It should work on most machines that have a working Korn Shell. It can usually also be made to work under the Bourne-Again Shell with only minor modifications.
An Apple Keynote theme file. It is an XML format and will work on any machine that has Apple Keynote installed.