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 .

B1: A compressed format similar to GZip but favoring speed over compression ratio. In particular, it will detect many file types that are already compressed and skip processing them to save time. It is an open format, and free applications and libraries exist to process it.
bar: The bar format is similar in concept to the tar format, but is not found on as many computer systems.
bat: A file with this extension is most likely a batch file for either CP/M or MS-DOS and is not likely to work on a different platform than the one for which it was originally written. It should be simple ASCII however, so it might be possible to figure out what it is supposed to do and write a new script to do the same.
bdf: The Bitmap Distribution Format is a format for storing bitmapped fonts. It is in simple ASCII. It originated on the X-Windows system but can be made to work on other systems as well. It is a product of Adobe.
bep: A file that has been compressed with geoBEAP. It can be used on GEOS systems that have geoBEAP installed.
blb & blorb: A single interactive fiction title may require numerous parts, including images, sounds, music, and of course an executable. A Blorb file simply packages them all together in a standardized way that can be recognized by most interactive fiction interpreters.
bmp: Microsoft bitmap image format. This is a fairly simple bitmap format that can be viewed on many different platforms but is directly supported by very few browsers. It is not used too much on the web (fortunately, as it is very inefficient) with GIFs, JPEGs, PNGs, and even X-bitmaps being preferred as they are much more portable. It is somewhat similar to the pict format.
bsh: Probably either a Bourne Shell script or a Bourne-Again Shell script. These are both pretty similar to each other, anyway (Bourne-Again is a superset of Bourne), and the Bourne-Again Shell is available for many different platforms.
bz2: The bzip2 compression program is similar in nature to both gzip and zip. It will often outperform the other two, but it is not yet particularly widespread and so is not usually the best choice for information that must be shared between different platforms.