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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
HD - Extension Details
Date Added: February 09, 2008
File Extension:  .HD
Description 1: .HD file extension is linked with HD Photo formerly known as Windows Media Photo or WMPhoto a file format that is used in storing photographic image bitmaps. Microsoft developed the DH photo format and it supports lossless and lossy compression. The image quality produced by DH Photo requires computational processing and small file sizes, but the overall quality is comparable to JPEG 2000. .HD file extension is also associated with Adobe Photoshop.
File Type:   Bitmap image file
Mode: Binary
Program(s) to Open:  Windows & Mac: HD Photo, Adobe Photoshop
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Extension: