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

CAB file extension

Windows Cabinet File

System Files

CBR file extension

Comic Book RAR Archive

Compressed Files

CGI file extension

Common Gateway Interface Script

Executable Files

CUE file extension

Cue Sheet File

Disk Image Files

FON file extension

Generic Font File

Font Files

GED file extension

GEDCOM Genealogy Data File

Data Files

HTML file extension

Hypertext Markup Language File

Web Files

M3U file extension

Media Playlist File

Audio Files

MPA file extension

MPEG-2 Audio File

Audio Files

NES file extension

Nintendo (NES) ROM File

Game Files

PKG file extension

Mac OS X Installer Package

Compressed Files

PRF file extension

Outlook Profile File

Settings Files

SYS file extension

Windows System File

System Files

TAX2012 file extension

TurboTax 2012 Tax Return

Data Files

UUE file extension

Uuencoded File

Encoded Files