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

AVI file extension

Audio Video Interleave File

Video Files

BMP file extension

Bitmap Image File

Raster Image Files

CLASS file extension

Java Class File

Developer Files

CSS file extension

Cascading Style Sheet

Web Files

DAT file extension

Data File

Data Files

DB file extension

Database File

Database Files

DLL file extension

Dynamic Link Library

System Files

DRV file extension

Device Driver

System Files

DTD file extension

Document Type Definition File

Developer Files

FLA file extension

Adobe Flash Animation

Developer Files

ICO file extension

Icon File

System Files

MDF file extension

Media Disc Image File

Disk Image Files

NES file extension

Nintendo (NES) ROM File

Game Files

PPS file extension

PowerPoint Slide Show

Data Files

WMV file extension

Windows Media Video File

Video Files