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

AI file extension

Adobe Illustrator File

Vector Image Files

ASX file extension

Microsoft ASF Redirector File

Video Files

AVI file extension

Audio Video Interleave File

Video Files

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

CSS file extension

Cascading Style Sheet

Web Files

DESKTHEMEPACK file extension

Windows 8 Desktop Theme Pack File

System Files

FLV file extension

Flash Video File

Video Files

KMZ file extension

Google Earth Placemark File

GIS Files

PAGES file extension

Pages Document

Text Files

PKG file extension

Mac OS X Installer Package

Compressed Files

PLUGIN file extension

Mac OS X Plug-in

Plugin Files

PNG file extension

Portable Network Graphic

Raster Image Files

SLN file extension

Visual Studio Solution File

Developer Files