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

APP file extension

Mac OS X Application

Executable Files

ASF file extension

Advanced Systems Format File

Video Files

C file extension

C/C++ Source Code File

Developer Files

EPS file extension

Encapsulated PostScript File

Vector Image Files

FON file extension

Generic Font File

Font Files

HTM file extension

Hypertext Markup Language File

Web Files

JS file extension

JavaScript File

Web Files

LOG file extension

Log File

Text Files

MDF file extension

Media Disc Image File

Disk Image Files

MPG file extension

MPEG Video File

Video Files

NES file extension

Nintendo (NES) ROM File

Game Files

PCT file extension

Picture File

Layout Files

SAV file extension

Saved Game

Game Files

TIFF file extension

Tagged Image File Format

Raster Image Files

WPD file extension

WordPerfect Document

Text Files