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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
FDF - Extension Details
Date Added: January 11, 2008
File Extension:  .FDF
Description 1: .FDF file extension is linked with Acrobat Forms Data Format. This file contains the data text format that is exported from .PDF form fields. .FDF files are smaller than .PDF files since they only contain form field data. .FDF files are created via Acrobat [select from the menu bar: Advanced > Forms > Export Forms Data]. .FDF files are created on web servers via .CGI scripts.
File Type:   Document File
Mode: Binary
Program(s) to Open:  Windows & Mac: Adobe Acrobat
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