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

CAB file extension

Windows Cabinet File

System Files

DAT file extension

Data File

Data Files

DEM file extension

Video Game Demo File

Game Files

DOCX file extension

Microsoft Word Open XML Document

Text Files

GAM file extension

Saved Game File

Game Files

LUA file extension

Lua Source File

Developer Files

MDF file extension

Media Disc Image File

Disk Image Files

MP3 file extension

MP3 Audio File

Audio Files

PDF file extension

Portable Document Format File

Layout Files

RAR file extension

WinRAR Compressed Archive

Compressed Files

RPM file extension

Red Hat Package Manager File

Compressed Files

TIF file extension

Tagged Image File

Raster Image Files

WMA file extension

Windows Media Audio File

Audio Files

XCODEPROJ file extension

Xcode Project

Developer Files

3DM file extension

Rhino 3D Model

3D Image Files