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

WSF file extension

Windows Script File

Executable Files

MP3 file extension

MP3 Audio File

Audio Files

PCT file extension

Picture File

Layout Files

SQL file extension

Structured Query Language Data File

Database Files

DXF file extension

Drawing Exchange Format File

CAD Files

CFG file extension

Configuration File

Settings Files

7Z file extension

7-Zip Compressed File

Compressed Files

AI file extension

Adobe Illustrator File

Vector Image Files

XCODEPROJ file extension

Xcode Project

Developer Files

PKG file extension

Mac OS X Installer Package

Compressed Files

OBJ file extension

Wavefront 3D Object File

3D Image Files

KML file extension

Keyhole Markup Language File

GIS Files

ZIPX file extension

Extended Zip File

Compressed Files

PHP file extension

PHP Source Code File

Web Files

MIM file extension

Multi-Purpose Internet Mail Message File

Encoded Files