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

AVI file extension

Audio Video Interleave File

Video Files

COM file extension

DOS Command File

Executable Files

CPL file extension

Windows Control Panel Item

System Files

DWG file extension

AutoCAD Drawing Database File

CAD Files

IBOOKS file extension

Multi-Touch iBook

Data Files

IFF file extension

Interchange File Format

Audio Files

INDD file extension

Adobe InDesign Document

Layout Files

M file extension

Objective-C Implementation File

Developer Files

MID file extension

MIDI File

Audio Files

OBJ file extension

Wavefront 3D Object File

3D Image Files

PART file extension

Partially Downloaded File

Misc Files

PSD file extension

Adobe Photoshop Document

Raster Image Files

RSS file extension

Rich Site Summary

Web Files

SLN file extension

Visual Studio Solution File

Developer Files

WAV file extension

WAVE Audio File

Audio Files