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

CSS file extension

Cascading Style Sheet

Web Files

DAT file extension

Data File

Data Files

DEB file extension

Debian Software Package

Compressed Files

DMP file extension

Windows Memory Dump

System Files

H file extension

C/C++/Objective-C Header File

Developer Files

JS file extension

JavaScript File

Web Files

KMZ file extension

Google Earth Placemark File

GIS Files

MP4 file extension

MPEG-4 Video File

Video Files

OTF file extension

OpenType Font

Font Files

PIF file extension

Program Information File

Executable Files

SRT file extension

SubRip Subtitle File

Video Files

TGA file extension

Targa Graphic

Raster Image Files

TMP file extension

Temporary File

Backup Files

3G2 file extension

3GPP2 Multimedia File

Video Files