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

APP file extension

Mac OS X Application

Executable Files

BAK file extension

Backup File

Backup Files

DEB file extension

Debian Software Package

Compressed Files

FON file extension

Generic Font File

Font Files

INDD file extension

Adobe InDesign Document

Layout Files

JPG file extension

JPEG Image

Raster Image Files

LNK file extension

Windows File Shortcut

System Files

M4V file extension

iTunes Video File

Video Files

PDF file extension

Portable Document Format File

Layout Files

PKG file extension

Mac OS X Installer Package

Compressed Files

SAV file extension

Saved Game

Game Files

SWF file extension

Shockwave Flash Movie

Video Files

TTF file extension

TrueType Font

Font Files

VB file extension

VBScript File

Executable Files

3DS file extension

3D Studio Scene

3D Image Files