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

C file extension

C/C++ Source Code File

Developer Files

CAB file extension

Windows Cabinet File

System Files

CER file extension

Internet Security Certificate

Web 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

DWG file extension

AutoCAD Drawing Database File

CAD Files

IFF file extension

Interchange File Format

Audio Files

KML file extension

Keyhole Markup Language File

GIS Files

MP3 file extension

MP3 Audio File

Audio Files

MP4 file extension

MPEG-4 Video File

Video Files

MSG file extension

Outlook Mail Message

Text Files

MSI file extension

Windows Installer Package

Misc Files

PAGES file extension

Pages Document

Text Files

PDB file extension

Program Database

Database Files