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The File Extension Library

What is a file extension?

Short answer: it's the set of letters after the period (.) in the name of a file.

Long answer: File extensions signify the file format of a file. It tells the operating system (OS) how data was stored in the file. Not all OS, require a file extension though. For instance, this is optional in Unix, but is mandatory with MS-DOS and Windows systems.

In most file formats the file type is actually defined by the contents (first bytes, file structure), but extensions are used to define the application that is used for opening the file.

Below is a detailed database of thousands of file extensions our team has compiled for you. Feel free to browse!


Browse all Extensions:
ABCDEFGHIJKLMNOPQRSTUVWXYZ
CG4 - Extension Details
Date Added: January 12, 2008
File Extension:  .CG4
Description 1: .CG4 file extension is linked with CALS Group IV Bitmap Graphics. This is the file extension for the bitmap graphics utilized by CALS Group IV. .CG4 is also associated with XnView a freeware utility for converting and viewing graphic files. XnView offers users the following features: resize, rotate and crop support; lossless crop and rotate support; modify colors; IPTC editing; import around 400 graphic file formats and export around 50 graphic file formats; support for multipage animated GIF and ICO, and TIFF; etc. XnView is owned and developed by Pierre Gougelet.
File Type:   Bitmap Image File
Mode: Binary
Program(s) to Open:  Windows & Mac: XnView
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