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

APK file extension

Android Package File

Executable Files

C file extension

C/C++ Source Code File

Developer Files

CBR file extension

Comic Book RAR Archive

Compressed Files

CGI file extension

Common Gateway Interface Script

Executable Files

CSS file extension

Cascading Style Sheet

Web Files

DEM file extension

Video Game Demo File

Game Files

DESKTHEMEPACK file extension

Windows 8 Desktop Theme Pack File

System Files

H file extension

C/C++/Objective-C Header File

Developer Files

KEYCHAIN file extension

Mac OS X Keychain File

Data Files

LOG file extension

Log File

Text Files

LUA file extension

Lua Source File

Developer Files

MOV file extension

Apple QuickTime Movie

Video Files

MPG file extension

MPEG Video File

Video Files

WPD file extension

WordPerfect Document

Text Files

3DS file extension

3D Studio Scene

3D Image Files