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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
JJ - Extension Details
Date Added: September 02, 2009
File Extension:  .JJ
Description 1: .JJ file extension is linked with JavaCC file. Java is a programming language released in 1995 and developed [originally] by Sun Microsystems. Most of Javas syntax are from C and C++, but has uncomplicated object model and lesser lowlevel facilities. Java became opensource software since 2006 under the terms of the GNU General Public License. Sun Microsystems made all of Javas core code/s free and opensource on 2007.
File Type:   Data File
Mode: ASCII
Program(s) to Open:  Windows & Mac: Java
Common:
Extension: