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

CGI file extension

Common Gateway Interface Script

Executable Files

CLASS file extension

Java Class File

Developer Files

DDS file extension

DirectDraw Surface

Raster Image Files

DMG file extension

Mac OS X Disk Image

Disk Image Files

FLA file extension

Adobe Flash Animation

Developer Files

FON file extension

Generic Font File

Font Files

GAM file extension

Saved Game File

Game Files

INDD file extension

Adobe InDesign Document

Layout Files

JPG file extension

JPEG Image

Raster Image Files

RSS file extension

Rich Site Summary

Web Files

TAX2012 file extension

TurboTax 2012 Tax Return

Data Files

VCD file extension

Virtual CD

Disk Image Files

WAV file extension

WAVE Audio File

Audio Files

ZIP file extension

Zipped File

Compressed Files

3G2 file extension

3GPP2 Multimedia File

Video Files