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

ASPX file extension

Active Server Page Extended File

Web Files

DEM file extension

Video Game Demo File

Game Files

DLL file extension

Dynamic Link Library

System Files

DMP file extension

Windows Memory Dump

System Files

DOCX file extension

Microsoft Word Open XML Document

Text Files

LUA file extension

Lua Source File

Developer Files

M3U file extension

Media Playlist File

Audio Files

PART file extension

Partially Downloaded File

Misc Files

PKG file extension

Mac OS X Installer Package

Compressed Files

RA file extension

Real Audio File

Audio Files

SLN file extension

Visual Studio Solution File

Developer Files

TGA file extension

Targa Graphic

Raster Image Files

THM file extension

Thumbnail Image File

Raster Image Files

VCXPROJ file extension

Visual C++ Project

Developer Files

YUV file extension

YUV Encoded Image File

Raster Image Files