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 .

Python Egg files are similar to JAR files but for Python rather than Java.
An Emacs LISP file is used to extend the capabilities of the popular Emacs editor. It is ASCII and will work on any machine with Emacs installed.
A Emacs LISP file (compiled) is used to extend the capabilities of the popular Emacs editor. It is a binary, compiled version of a .el file.
An MS-Windows enhanced metafile is like an ordinary CGM metafile but with extensions that make it specific to MS-Windows, and it will not work on most other machines without conversion.
An encapsulated Postscript file is often a combination of Postscript and various miscellaneous image file formats and is often difficult to use on a set up that is different from the one on which it was created.
An Adobe e-book download file is not an e-book itself but rather a series of instructions that a computer will be able to use to download an e-book and load it into an e-book reader. It is binary and not particularly portable.
An executable is a program for a CP/M, MS-DOS, MS-Windows, or possibly even an x86 GEOS machine. It will probably not work on a platform other than the one for which it was designed (including the different variants of MS-Windows). Similar to, but usually larger than, a com file.