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

MP4 file extension

MPEG-4 Video File

Video Files

AIF file extension

Audio Interchange File Format

Audio Files

KML file extension

Keyhole Markup Language File

GIS Files

PKG file extension

Mac OS X Installer Package

Compressed Files

TIFF file extension

Tagged Image File Format

Raster Image Files

7Z file extension

7-Zip Compressed File

Compressed Files

MOBI file extension

Mobipocket eBook

eBook Files

MPG file extension

MPEG Video File

Video Files

JAR file extension

Java Archive File

Executable Files

CRX file extension

Chrome Extension

Plugin Files

TXT file extension

Plain Text File

Text Files

DMG file extension

Mac OS X Disk Image

Disk Image Files

WPS file extension

Microsoft Works Word Processor Document

Text Files

ICO file extension

Icon File

System Files

EPS file extension

Encapsulated PostScript File

Vector Image Files