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

BAT file extension

DOS Batch File

Executable Files

CFM file extension

ColdFusion Markup File

Web Files

CLASS file extension

Java Class File

Developer Files

CPP file extension

C++ Source Code File

Developer Files

CRDOWNLOAD file extension

Chrome Partially Downloaded File

Misc Files

CRX file extension

Chrome Extension

Plugin Files

DB file extension

Database File

Database Files

DOCX file extension

Microsoft Word Open XML Document

Text Files

KEYCHAIN file extension

Mac OS X Keychain File

Data Files

KML file extension

Keyhole Markup Language File

GIS Files

M3U file extension

Media Playlist File

Audio Files

MSI file extension

Windows Installer Package

Misc Files

PIF file extension

Program Information File

Executable Files

PKG file extension

Mac OS X Installer Package

Compressed Files

PSPIMAGE file extension

PaintShop Pro Image

Raster Image Files