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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
H1K - Extension Details
Date Added: February 10, 2008
File Extension:  .H1K
Description 1: .H1K file extension is linked with Keyword Index Microsoft Windows Assistance Platform client help related file. .H1K file is utilized by Windows to create Help project indexes. .H1K file is comparable to Microsoft Help 2.x .HxK file. Windows Vista has a new Help engine, HelpPane.exe or Assistance Platform Client, which is not compatible to other versions of Windows. This exclusive platform is a requisite of Help Files with .H1S file extension.
File Type:   System File
Mode: Binary
Program(s) to Open:  Windows: Windows Vista Help File
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