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

GAM file extension

Saved Game File

Game Files

TAR file extension

Consolidated Unix File Archive

Data Files

SLN file extension

Visual Studio Solution File

Developer Files

MP3 file extension

MP3 Audio File

Audio Files

DEB file extension

Debian Software Package

Compressed Files

LUA file extension

Lua Source File

Developer Files

HTML file extension

Hypertext Markup Language File

Web Files

DLL file extension

Dynamic Link Library

System Files

CSS file extension

Cascading Style Sheet

Web Files

PKG file extension

Mac OS X Installer Package

Compressed Files

7Z file extension

7-Zip Compressed File

Compressed Files

GPX file extension

GPS Exchange File

GIS Files

TMP file extension

Temporary File

Backup Files

ODT file extension

OpenDocument Text Document

Text Files

ICO file extension

Icon File

System Files