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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
THUMB - Extension Details
Date Added: April 02, 2009
File Extension:  .THUMB
Description 1: A file with the .THUMB extension contains small thumbnail images that the photo gallery program freeware JAlbum generates. THUMB files are created from fullsize images and serve to represent the original images in a particular album. With the .THUMB file format, it is possible to browse multiple photos at a time.
File Type:   Raster Image file
Mode: Binary
Program(s) to Open:  Mac, Windows and Unix: Jalbum
Common:
Extension: