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

CPL file extension

Windows Control Panel Item

System Files

DOCX file extension

Microsoft Word Open XML Document

Text Files

EXE file extension

Windows Executable File

Executable Files

FLV file extension

Flash Video File

Video Files

ICNS file extension

Mac OS X Icon Resource File

System Files

KML file extension

Keyhole Markup Language File

GIS Files

MP3 file extension

MP3 Audio File

Audio Files

MSG file extension

Outlook Mail Message

Text Files

NES file extension

Nintendo (NES) ROM File

Game Files

PNG file extension

Portable Network Graphic

Raster Image Files

SAV file extension

Saved Game

Game Files

SRT file extension

SubRip Subtitle File

Video Files

TOAST file extension

Toast Disc Image

Disk Image Files

VCD file extension

Virtual CD

Disk Image Files

WSF file extension

Windows Script File

Executable Files