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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
ICQ - Extension Details
Date Added: March 11, 2008
File Extension:  .ICQ
Description 1: .ICQ file extension is linked with ICQ Archive File. This file extension is used for archive files or exported address book in ICQ [probably used in older versions]. ICQ is a communication application that allows users to interact and meet via instant messaging services it provides such as: voice, text, VoIP, video, community and entertainment products. .ICQ file extension and ICQ are owned and developed by ICQ LLC.
File Type:   Data File
Mode: ASCII
Program(s) to Open:  Windows & Mac: ICQ
Common:
Extension: