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

COM file extension

DOS Command File

Executable Files

CSV file extension

Comma Separated Values File

Data Files

DRV file extension

Device Driver

System Files

GBR file extension

Gerber File

Data Files

ICO file extension

Icon File

System Files

JS file extension

JavaScript File

Web Files

KEYCHAIN file extension

Mac OS X Keychain File

Data Files

M file extension

Objective-C Implementation File

Developer Files

M3U file extension

Media Playlist File

Audio Files

PKG file extension

Mac OS X Installer Package

Compressed Files

PPTX file extension

PowerPoint Open XML Presentation

Data Files

RM file extension

Real Media File

Video Files

SITX file extension

StuffIt X Archive

Compressed Files

SWF file extension

Shockwave Flash Movie

Video Files

XLR file extension

Works Spreadsheet

Spreadsheet Files