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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
XLS - Extension Details
Date Added: January 01, 1970
File Extension:  .XLS
Description 1: .XLS is the extension associated with Microsoft Excels spreadsheet. Microsoft Excel is the popular spreadsheet program that is capable of storing data in tables with columns and rows. Table cells can either contain results calculated from data of other cells or feature manually entered data. Creating graphs and charts is likewise possible using the same data found in the cells.
File Type:   Data file
Mode: ASCII
Program(s) to Open:  Windows: Nuance OmniPage Professional, Microsoft Excel or Excel Viewer Macintosh: Nuance OmniPage Pro X, Microsoft Excel
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