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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
XPI - Extension Details
Date Added: January 01, 1970
File Extension:  .XPI
Description 1: .XPI files deal with a compressed installation archive containing the main components that are installed in Mozilla and Firefox web browsers. These files are put in and installed by the Mozilla installer script. The XPI file format is also used for the installation of web browser extensions. XPI files are typically installed using draganddrop. Dragging and dropping the XPI files onto an open Internet browser window is all it takes.
File Type:   Compressed file
Mode: Binary
Program(s) to Open:  Mac and Windows: XPInstall (included with Firefox or Mozilla)
Common:
Extension: