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

CLASS file extension

Java Class File

Developer Files

CUE file extension

Cue Sheet File

Disk Image Files

FNT file extension

Windows Font File

Font Files

GAM file extension

Saved Game File

Game Files

GIF file extension

Graphical Interchange Format File

Raster Image Files

ICNS file extension

Mac OS X Icon Resource File

System Files

JSP file extension

Java Server Page

Web Files

KML file extension

Keyhole Markup Language File

GIS Files

M4V file extension

iTunes Video File

Video Files

PIF file extension

Program Information File

Executable Files

ROM file extension

N64 Game ROM File

Game Files

SITX file extension

StuffIt X Archive

Compressed Files

SWF file extension

Shockwave Flash Movie

Video Files

TMP file extension

Temporary File

Backup Files

WMA file extension

Windows Media Audio File

Audio Files