File extensions – definition and basic information


File extensions are the integral parts of the files that are on each computer. Often, when working on a computer, we encounter a wide range of files, such as docx, ppt, part, mp3 or rmvb. We realize that they are there – but we often do not know what they are for on our computer.

File extension, also known as the filename extension is a suffix added to the name of a computer file, usually consisting of a number of characters placed after the last dot in the filename, which gives us information about its coding. In other words a file extension is a file format. It allows the operating system (e.g. Windows) to recognize what program it should try to open the file.

In the table below you will find a random selection of popular file extensions.


File extension The full name of the file Category

ASP file extension

Active Server Page

Web Files

FON file extension

Generic Font File

Font Files

ASF file extension

Advanced Systems Format File

Video Files

ICNS file extension

Mac OS X Icon Resource File

System Files

7Z file extension

7-Zip Compressed File

Compressed Files

TAX2012 file extension

TurboTax 2012 Tax Return

Data Files

ASX file extension

Microsoft ASF Redirector File

Video Files

XCODEPROJ file extension

Xcode Project

Developer Files

PLUGIN file extension

Mac OS X Plug-in

Plugin Files

ODT file extension

OpenDocument Text Document

Text Files

SITX file extension

StuffIt X Archive

Compressed Files

VCD file extension

Virtual CD

Disk Image Files

CRX file extension

Chrome Extension

Plugin Files

SAV file extension

Saved Game

Game Files

C file extension

C/C++ Source Code File

Developer Files