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

APK file extension

Android Package File

Executable Files

CLASS file extension

Java Class File

Developer Files

DMG file extension

Mac OS X Disk Image

Disk Image Files

GADGET file extension

Windows Gadget

Executable Files

IBOOKS file extension

Multi-Touch iBook

Data Files

ICS file extension

iCalendar File

Misc Files

MDB file extension

Microsoft Access Database

Database Files

PKG file extension

Mac OS X Installer Package

Compressed Files

PPT file extension

PowerPoint Presentation

Data Files

SAV file extension

Saved Game

Game Files

SDF file extension

Standard Data File

Data Files

TXT file extension

Plain Text File

Text Files

WMV file extension

Windows Media Video File

Video Files

XCODEPROJ file extension

Xcode Project

Developer Files

3GP file extension

3GPP Multimedia File

Video Files