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

APP file extension

Mac OS X Application

Executable Files

CGI file extension

Common Gateway Interface Script

Executable Files

CRX file extension

Chrome Extension

Plugin Files

CSV file extension

Comma Separated Values File

Data Files

DMG file extension

Mac OS X Disk Image

Disk Image Files

JAR file extension

Java Archive File

Executable Files

KML file extension

Keyhole Markup Language File

GIS Files

M3U file extension

Media Playlist File

Audio Files

MDB file extension

Microsoft Access Database

Database Files

OTF file extension

OpenType Font

Font Files

PNG file extension

Portable Network Graphic

Raster Image Files

SYS file extension

Windows System File

System Files

TGA file extension

Targa Graphic

Raster Image Files

VCXPROJ file extension

Visual C++ Project

Developer Files

XLR file extension

Works Spreadsheet

Spreadsheet Files