Glossary of Computer File Formats
Don't know PDF from PNG? Use our word list to figure out what type of file you're dealing with—and which software will open it.
We've all received a computer file we didn't know how to open. The secret to identifying a compatible software program lies in the three- or four-letter extension at the end of the file name—which, for many of us, is a meaningless alphabet soup. This glossary will help you unscramble the mystery letters.


Audio Video Interleave. Most often played on Apple QuickTime or Windows Media Player, this format for sound and video clips is becoming obsolete.
Windows bitmap. These image files tend to be large because they are uncompressed; they have wide acceptance in all Windows systems.

If you use Microsoft Word to type genealogy notes or correspondence, the resulting files are DOCs.

Legacy Family Tree genealogy software's native file format.

Family Tree Maker software's native file format.

GEDCOM (short for Genealogical Data Communication). When genealogists who use different family tree programs want to share family files, they can convert their data to this standard file format any genealogy software can open.

Graphics Interchange Format. Most image-editing software, such as Adobe Photoshop Elements or Jasc Paint Shop Pro, can open this graphics format for still and animated images. Excellent for simple images that contain text, it's most often used for simple Web graphics with a small number of colors (not photos).

Hypertext Markup Language. This is the predominant programming language for Web pages. Open an HTML file in Internet Explorer or another Web browser to view the "finished" page; use an HTML or plain-text editor such as Notepad to see or change the coding.

Also JPEG, it's short for Joint Photographic Experts Group. JPG has become the most widely used format for static photographic images because it can display millions of colors. Any image-editing software can read a JPG.

Apple Quicktime Movie. MOV is probably the most common multimedia format for saving video or movie files, and is compatible with both Macintosh and Windows platforms.

One of the most popular audio formats, MP3 compresses sound clips into small files without losing quality. You can play MP3s on a portable device such as an iPod, or software such as iTunes and Real Player.

Moving Picture Experts Group. Any Mac or Windows video player can read this video format, popular for creating movies that get distributed over the Internet. The related MPEG-4 format uses separate compression for audio and video tracks.

Data files created by Personal Ancestral File software. Several other genealogy software programs, including Family Tree Maker, Legacy and RootsMagic, can import PAF files directly.

Portable Document Format. Created to ease document exchange, PDF lets you view a file exactly as designed without the program that created it. All you need is the free Adobe Reader.

The extension for files created by The Master Genealogist software, which can directly import the native file formats of most popular genealogy programs.

Portable Network Graphics. Developed as a replacement for GIF—and used for the same types of files—PNG compresses better, resulting in a smaller-size files of equal quality. Most image-editing software can open PNG files.
Photoshop Document. Adobe Photoshop's native format allows for preservation of layers, masks and profiles used in image editing.
Certain digital cameras support this "raw" image format, which uses nearly lossless compression while still being smaller than TIFF format photos. It is sometimes called DNG (Adobe's Digital Negative format).

RootsMagic genealogy software's native file format.

A file compressed by StuffIt software. SIT files were originally Mac-only, but now Windows can create and open them, too. Note that SIT and ZIP (below) shrink down other file formats for exchanging or archiving. You still need the applicable software to view the original files once you've "unstuffed" them.
Truevision Advanced Raster Graphics Adapter. Used for raster images, such as in video games.
Tagged Image File Format. Good for bitmap (pixel-based) images, such as photographs. Since TIFF produces large files, it's excellent if the end use is print (not Web) or archival.

Refers to plain-text files with little formatting; for example, no bold or italics. This format is most commonly used in simple text editors such as Windows Notepad and Mac TextEdit, but you can open them in almost any program that that can read a plain-text file (including word processors), making them good for file sharing.

Short for waveform, WAV is the standard format for storing audio on a PC. You can play WAV files on Windows or Mac in a program such as Windows Media Player or iTunes.

Windows Media Audio. WMA produces smaller files than WAV, but you can listen to them on similar software, including Windows Media Player and RealPlayer.
Windows Media Video. Used for internet video, this file format must be read with Windows Media Player or an application such as RealPlayer. Flip4Mac offers conversion for Mac users.

Similar to SIT, ZIP format uses Zip compression to compress a document or documents into one smaller file for sharing or archiving. Windows users can create ZIP files using a program such as WINZIP, while Mac OSX users can simply Control-click a file and select Create Archive of "file name".