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

AIF file extension

Audio Interchange File Format

Audio Files

APK file extension

Android Package File

Executable Files

CER file extension

Internet Security Certificate

Web Files

FON file extension

Generic Font File

Font Files

GIF file extension

Graphical Interchange Format File

Raster Image Files

GZ file extension

Gnu Zipped Archive

Compressed Files

IBOOKS file extension

Multi-Touch iBook

Data Files

INDD file extension

Adobe InDesign Document

Layout Files

JS file extension

JavaScript File

Web Files

MOV file extension

Apple QuickTime Movie

Video Files

RSS file extension

Rich Site Summary

Web Files

SITX file extension

StuffIt X Archive

Compressed Files

TMP file extension

Temporary File

Backup Files

TORRENT file extension

BitTorrent File

Misc Files

XML file extension

XML File

Data Files