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

WMV file extension

Windows Media Video File

Video Files

CFG file extension

Configuration File

Settings Files

7Z file extension

7-Zip Compressed File

Compressed Files

DMP file extension

Windows Memory Dump

System Files

RM file extension

Real Media File

Video Files

CBR file extension

Comic Book RAR Archive

Compressed Files

MID file extension

MIDI File

Audio Files

DB file extension

Database File

Database Files

DLL file extension

Dynamic Link Library

System Files

MIM file extension

Multi-Purpose Internet Mail Message File

Encoded Files

APP file extension

Mac OS X Application

Executable Files

ODT file extension

OpenDocument Text Document

Text Files

CLASS file extension

Java Class File

Developer Files

PLUGIN file extension

Mac OS X Plug-in

Plugin Files

FNT file extension

Windows Font File

Font Files