Subscribe to our newsletter:

Filename Extension Reference

iPhone / iPad
  • Reference
I want this app
Download from AppStore

Extensions are for more than just hair! Traditionally, every file created by a computer application ends with an extension. Usually three letters or less, an extension identifies which application uses the file and sometimes what kind of data is in it. Over the decades, a staggering number of often cryptic file extensions have been created. If you find an unknown file deep in the recesses of a computer and aren't sure what it contains, where it came from, or which application created it, Extensions will help!

The Extensions application for the iPhone contains a database of over 3200 extensions. You can quickly browse through its alphabetized list of extensions using the quick index on the side. Tapping the search button allows you to search for the name of an abbreviation or its definition at the same time. The description of each file extension is shown below the extension in the list at all times. Descriptions that are too long to fit are shortened with an ellipsis (...) at the end. Simply tapping on an extension will show the full description where you can tap the star to add that extension to your favorites list for easy access in the future.

Features in version 1.0
• Over 3200 extensions
• Star important extensions to your favorites list
• Fast search while typing
• Search extensions and descriptions at the same time
• Abbreviation definitions are shown at all times
• Easy browsing with the index
• Abbreviations are sorted and grouped by first letter

New extensions will be added to the application with future updates. The Extensions application uses a community-supported database of filename extensions. To suggest extensions to the database or provide feature requests, please email us at