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

C file extension

C/C++ Source Code File

Developer Files

CRX file extension

Chrome Extension

Plugin Files

CS file extension

Visual C# Source Code File

Developer Files

DEM file extension

Video Game Demo File

Game Files

FON file extension

Generic Font File

Font Files

INDD file extension

Adobe InDesign Document

Layout Files

KEYCHAIN file extension

Mac OS X Keychain File

Data Files

MOV file extension

Apple QuickTime Movie

Video Files

PNG file extension

Portable Network Graphic

Raster Image Files

RPM file extension

Red Hat Package Manager File

Compressed Files

SQL file extension

Structured Query Language Data File

Database Files

TARGZ file extension

Compressed Tarball File

Compressed Files

VCD file extension

Virtual CD

Disk Image Files

WMV file extension

Windows Media Video File

Video Files

3G2 file extension

3GPP2 Multimedia File

Video Files