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

BAT file extension

DOS Batch File

Executable Files

CRDOWNLOAD file extension

Chrome Partially Downloaded File

Misc Files

CS file extension

Visual C# Source Code File

Developer Files

DESKTHEMEPACK file extension

Windows 8 Desktop Theme Pack File

System Files

HQX file extension

BinHex 4.0 Encoded File

Encoded Files

KML file extension

Keyhole Markup Language File

GIS Files

M3U file extension

Media Playlist File

Audio Files

OTF file extension

OpenType Font

Font Files

PIF file extension

Program Information File

Executable Files

PPT file extension

PowerPoint Presentation

Data Files

PSD file extension

Adobe Photoshop Document

Raster Image Files

TAX2012 file extension

TurboTax 2012 Tax Return

Data Files

WAV file extension

WAVE Audio File

Audio Files

XCODEPROJ file extension

Xcode Project

Developer Files

3DS file extension

3D Studio Scene

3D Image Files