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

BAT file extension

DOS Batch File

Executable Files

EPS file extension

Encapsulated PostScript File

Vector Image Files

FLV file extension

Flash Video File

Video Files

ICO file extension

Icon File

System Files

IFF file extension

Interchange File Format

Audio Files

KEYCHAIN file extension

Mac OS X Keychain File

Data Files

M3U file extension

Media Playlist File

Audio Files

M4A file extension

MPEG-4 Audio File

Audio Files

MDF file extension

Media Disc Image File

Disk Image Files

MID file extension

MIDI File

Audio Files

ODT file extension

OpenDocument Text Document

Text Files

SAV file extension

Saved Game

Game Files

SITX file extension

StuffIt X Archive

Compressed Files

TOAST file extension

Toast Disc Image

Disk Image Files

VCF file extension

vCard File

Data Files