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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
A21 - Extension Details
Date Added: January 01, 1970
File Extension:  .A21
Description 1: .A21 file extension is linked with Soundweb Firmware and it is owned by BSS Audio. Soundweb is a DSP system application that allows users to process any audio system design from one single unit. .A21 file extension works in conjunction with a .DIS file, and it is an audio and music file extension.
File Type:   Audio/Music File
Mode: Binary
Program(s) to Open:  Soundweb Firmware
Common:
Extension: