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

CSV file extension

Comma Separated Values File

Data Files

DAT file extension

Data File

Data Files

DEM file extension

Video Game Demo File

Game Files

H file extension

C/C++/Objective-C Header File

Developer Files

KEYCHAIN file extension

Mac OS X Keychain File

Data Files

LUA file extension

Lua Source File

Developer Files

M3U file extension

Media Playlist File

Audio Files

M4V file extension

iTunes Video File

Video Files

MDF file extension

Media Disc Image File

Disk Image Files

RAR file extension

WinRAR Compressed Archive

Compressed Files

SYS file extension

Windows System File

System Files

VCF file extension

vCard File

Data Files

WMA file extension

Windows Media Audio File

Audio Files

WMV file extension

Windows Media Video File

Video Files

ZIPX file extension

Extended Zip File

Compressed Files