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

DEM file extension

Video Game Demo File

Game Files

MID file extension

MIDI File

Audio Files

DEB file extension

Debian Software Package

Compressed Files

CFM file extension

ColdFusion Markup File

Web Files

XCODEPROJ file extension

Xcode Project

Developer Files

MP3 file extension

MP3 Audio File

Audio Files

DLL file extension

Dynamic Link Library

System Files

IFF file extension

Interchange File Format

Audio Files

HTML file extension

Hypertext Markup Language File

Web Files

TMP file extension

Temporary File

Backup Files

PSD file extension

Adobe Photoshop Document

Raster Image Files

7Z file extension

7-Zip Compressed File

Compressed Files

PSPIMAGE file extension

PaintShop Pro Image

Raster Image Files

KML file extension

Keyhole Markup Language File

GIS Files

MSG file extension

Outlook Mail Message

Text Files