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

AIF file extension

Audio Interchange File Format

Audio Files

CER file extension

Internet Security Certificate

Web Files

CFG file extension

Configuration File

Settings Files

COM file extension

DOS Command File

Executable Files

DLL file extension

Dynamic Link Library

System Files

FNT file extension

Windows Font File

Font Files

KEY file extension

Keynote Presentation

Data Files

ROM file extension

N64 Game ROM File

Game Files

RSS file extension

Rich Site Summary

Web Files

SAV file extension

Saved Game

Game Files

TEX file extension

LaTeX Source Document

Text Files

WSF file extension

Windows Script File

Executable Files

XCODEPROJ file extension

Xcode Project

Developer Files

XML file extension

XML File

Data Files

3DM file extension

Rhino 3D Model

3D Image Files