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

CER file extension

Internet Security Certificate

Web Files

CUE file extension

Cue Sheet File

Disk Image Files

DEB file extension

Debian Software Package

Compressed Files

DMG file extension

Mac OS X Disk Image

Disk Image Files

GAM file extension

Saved Game File

Game Files

GZ file extension

Gnu Zipped Archive

Compressed Files

JPG file extension

JPEG Image

Raster Image Files

M file extension

Objective-C Implementation File

Developer Files

MAX file extension

3ds Max Scene File

3D Image Files

NES file extension

Nintendo (NES) ROM File

Game Files

PKG file extension

Mac OS X Installer Package

Compressed Files

PNG file extension

Portable Network Graphic

Raster Image Files

PPS file extension

PowerPoint Slide Show

Data Files

RM file extension

Real Media File

Video Files

SQL file extension

Structured Query Language Data File

Database Files