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

APK file extension

Android Package File

Executable Files

CFM file extension

ColdFusion Markup File

Web Files

CPP file extension

C++ Source Code File

Developer Files

CRX file extension

Chrome Extension

Plugin Files

DESKTHEMEPACK file extension

Windows 8 Desktop Theme Pack File

System Files

DLL file extension

Dynamic Link Library

System Files

GBR file extension

Gerber File

Data Files

HTML file extension

Hypertext Markup Language File

Web Files

ICNS file extension

Mac OS X Icon Resource File

System Files

ICO file extension

Icon File

System Files

KEY file extension

Keynote Presentation

Data Files

M4A file extension

MPEG-4 Audio File

Audio Files

PNG file extension

Portable Network Graphic

Raster Image Files

RSS file extension

Rich Site Summary

Web Files

WAV file extension

WAVE Audio File

Audio Files