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

ASP file extension

Active Server Page

Web Files

AVI file extension

Audio Video Interleave File

Video Files

DLL file extension

Dynamic Link Library

System Files

GAM file extension

Saved Game File

Game Files

IFF file extension

Interchange File Format

Audio Files

LUA file extension

Lua Source File

Developer Files

MDF file extension

Media Disc Image File

Disk Image Files

MIM file extension

Multi-Purpose Internet Mail Message File

Encoded Files

PART file extension

Partially Downloaded File

Misc Files

PLUGIN file extension

Mac OS X Plug-in

Plugin Files

PS file extension

PostScript File

Vector Image Files

SDF file extension

Standard Data File

Data Files

SYS file extension

Windows System File

System Files

TXT file extension

Plain Text File

Text Files

VCD file extension

Virtual CD

Disk Image Files