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

7Z file extension

7-Zip Compressed File

Compressed Files

MOV file extension

Apple QuickTime Movie

Video Files

PHP file extension

PHP Source Code File

Web Files

NES file extension

Nintendo (NES) ROM File

Game Files

DMG file extension

Mac OS X Disk Image

Disk Image Files

DLL file extension

Dynamic Link Library

System Files

M3U file extension

Media Playlist File

Audio Files

CPL file extension

Windows Control Panel Item

System Files

TARGZ file extension

Compressed Tarball File

Compressed Files

SRT file extension

SubRip Subtitle File

Video Files

HQX file extension

BinHex 4.0 Encoded File

Encoded Files

3GP file extension

3GPP Multimedia File

Video Files

WMV file extension

Windows Media Video File

Video Files

RAR file extension

WinRAR Compressed Archive

Compressed Files

PART file extension

Partially Downloaded File

Misc Files