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

DLL file extension

Dynamic Link Library

System Files

DMG file extension

Mac OS X Disk Image

Disk Image Files

FLA file extension

Adobe Flash Animation

Developer Files

ICNS file extension

Mac OS X Icon Resource File

System Files

KEY file extension

Keynote Presentation

Data Files

MSG file extension

Outlook Mail Message

Text Files

OTF file extension

OpenType Font

Font Files

RAR file extension

WinRAR Compressed Archive

Compressed Files

SAV file extension

Saved Game

Game Files

SITX file extension

StuffIt X Archive

Compressed Files

TGA file extension

Targa Graphic

Raster Image Files

VB file extension

VBScript File

Executable Files

WMA file extension

Windows Media Audio File

Audio Files

3DS file extension

3D Studio Scene

3D Image Files