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

CAB file extension

Windows Cabinet File

System Files

CFM file extension

ColdFusion Markup File

Web Files

CPP file extension

C++ Source Code File

Developer Files

IBOOKS file extension

Multi-Touch iBook

Data Files

INDD file extension

Adobe InDesign Document

Layout Files

M4V file extension

iTunes Video File

Video Files

MID file extension

MIDI File

Audio Files

MP3 file extension

MP3 Audio File

Audio Files

MPA file extension

MPEG-2 Audio File

Audio Files

MSI file extension

Windows Installer Package

Misc Files

SDF file extension

Standard Data File

Data Files

TAR file extension

Consolidated Unix File Archive

Data Files

TGA file extension

Targa Graphic

Raster Image Files

XLS file extension

Excel Spreadsheet

Spreadsheet Files