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

CFM file extension

ColdFusion Markup File

Web Files

CLASS file extension

Java Class File

Developer Files

CPP file extension

C++ Source Code File

Developer Files

CSR file extension

Certificate Signing Request File

Web Files

DOC# file extension

Microsoft Word Document

Text Files

GAM file extension

Saved Game File

Game Files

IFF file extension

Interchange File Format

Audio Files

KML file extension

Keyhole Markup Language File

GIS Files

M3U file extension

Media Playlist File

Audio Files

M4V file extension

iTunes Video File

Video Files

MDB file extension

Microsoft Access Database

Database Files

PAGES file extension

Pages Document

Text Files

TIFF file extension

Tagged Image File Format

Raster Image Files

WSF file extension

Windows Script File

Executable Files

XCODEPROJ file extension

Xcode Project

Developer Files