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

MP4 file extension

MPEG-4 Video File

Video Files

CFM file extension

ColdFusion Markup File

Web Files

CSS file extension

Cascading Style Sheet

Web Files

PKG file extension

Mac OS X Installer Package

Compressed Files

CPP file extension

C++ Source Code File

Developer Files

GAM file extension

Saved Game File

Game Files

7Z file extension

7-Zip Compressed File

Compressed Files

ISO file extension

Disc Image File

Disk Image Files

FON file extension

Generic Font File

Font Files

ASF file extension

Advanced Systems Format File

Video Files

AIF file extension

Audio Interchange File Format

Audio Files

JSP file extension

Java Server Page

Web Files

DOC file extension

Microsoft Word Document

Text Files

MID file extension

MIDI File

Audio Files

CUR file extension

Windows Cursor

System Files