What are File Extensions?A filename extension (or file type) is a suffix appended to the name of a computer file that indicates the encoding convention (file format) of its contents. The file type follows the ‘dot’ (e.g. .doc, .pdf, etc.) and is usually 3 or 4 characters in length.

A simpler explanation is that a filename extension indicates which software application created the file. Microsoft Operating Systems requires a file to have an extension. Other operating systems (e.g. Linux) do not require a file to have an extension.When you create and save a file, the extension is usually appended to the file automatically.

If you remove the filename extension from a file name, you may corrupt the file and render it unusable.

The following slides list some common filename extensions you may have encountered before:

Here are some common filename extensions you may have encountered before:

.jpeg Joint Photographic Experts Group

commonly used graphics file typea jpeg will usually take on the icon assigned to that file

extension by the software that created it.

.mpeg Moving Picture Experts Group

commonly used video file type

.wav Waveform audio format

commonly used sound file

.mp3 MPEG-1 Audio Layer 3

commonly used sound file

The compression protocols on this file type make it ideal for fast downloading and playback of music

.pptPowerPoint Template

MS PowerPoint fileCommonly Used MS Presentation Application

.xls MS Excel Spreadsheet

.docMS Word Document

Word Processing(Word 2007 files have a .docx extension)