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

CUE file extension

Cue Sheet File

Disk Image Files

DEM file extension

Video Game Demo File

Game Files

DESKTHEMEPACK file extension

Windows 8 Desktop Theme Pack File

System Files

DLL file extension

Dynamic Link Library

System Files

DRV file extension

Device Driver

System Files

GZ file extension

Gnu Zipped Archive

Compressed Files

INDD file extension

Adobe InDesign Document

Layout Files

LOG file extension

Log File

Text Files

MID file extension

MIDI File

Audio Files

NES file extension

Nintendo (NES) ROM File

Game Files

OBJ file extension

Wavefront 3D Object File

3D Image Files

PNG file extension

Portable Network Graphic

Raster Image Files

TARGZ file extension

Compressed Tarball File

Compressed Files

TIFF file extension

Tagged Image File Format

Raster Image Files

VCD file extension

Virtual CD

Disk Image Files