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

GZ file extension

Gnu Zipped Archive

Compressed Files

IBOOKS file extension

Multi-Touch iBook

Data Files

CS file extension

Visual C# Source Code File

Developer Files

NES file extension

Nintendo (NES) ROM File

Game Files

RM file extension

Real Media File

Video Files

M4A file extension

MPEG-4 Audio File

Audio Files

FON file extension

Generic Font File

Font Files

7Z file extension

7-Zip Compressed File

Compressed Files

MIM file extension

Multi-Purpose Internet Mail Message File

Encoded Files

PIF file extension

Program Information File

Executable Files

FNT file extension

Windows Font File

Font Files

CGI file extension

Common Gateway Interface Script

Executable Files

KEYCHAIN file extension

Mac OS X Keychain File

Data Files

RAR file extension

WinRAR Compressed Archive

Compressed Files

GED file extension

GEDCOM Genealogy Data File

Data Files