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

AVI file extension

Audio Video Interleave File

Video Files

BMP file extension

Bitmap Image File

Raster Image Files

CFM file extension

ColdFusion Markup File

Web Files

CGI file extension

Common Gateway Interface Script

Executable Files

CSV file extension

Comma Separated Values File

Data Files

DBF file extension

Database File

Database Files

FON file extension

Generic Font File

Font Files

ICO file extension

Icon File

System Files

INI file extension

Windows Initialization File

Settings Files

KMZ file extension

Google Earth Placemark File

GIS Files

M4V file extension

iTunes Video File

Video Files

PNG file extension

Portable Network Graphic

Raster Image Files

PPTX file extension

PowerPoint Open XML Presentation

Data Files

RSS file extension

Rich Site Summary

Web Files