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

CFM file extension

ColdFusion Markup File

Web Files

CLASS file extension

Java Class File

Developer Files

DNG file extension

Digital Negative Image File

Camera Raw Files

IFF file extension

Interchange File Format

Audio Files

OBJ file extension

Wavefront 3D Object File

3D Image Files

PHP file extension

PHP Source Code File

Web Files

PKG file extension

Mac OS X Installer Package

Compressed Files

RSS file extension

Rich Site Summary

Web Files

SAV file extension

Saved Game

Game Files

SDF file extension

Standard Data File

Data Files

SVG file extension

Scalable Vector Graphics File

Vector Image Files

YUV file extension

YUV Encoded Image File

Raster Image Files

3G2 file extension

3GPP2 Multimedia File

Video Files