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

EPS file extension

Encapsulated PostScript File

Vector Image Files

DRV file extension

Device Driver

System Files

ICNS file extension

Mac OS X Icon Resource File

System Files

DLL file extension

Dynamic Link Library

System Files

CPP file extension

C++ Source Code File

Developer Files

LUA file extension

Lua Source File

Developer Files

GIF file extension

Graphical Interchange Format File

Raster Image Files

JPG file extension

JPEG Image

Raster Image Files

7Z file extension

7-Zip Compressed File

Compressed Files

PCT file extension

Picture File

Layout Files

SRT file extension

SubRip Subtitle File

Video Files

KML file extension

Keyhole Markup Language File

GIS Files

VCD file extension

Virtual CD

Disk Image Files

SDF file extension

Standard Data File

Data Files

ZIPX file extension

Extended Zip File

Compressed Files