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

AVI file extension

Audio Video Interleave File

Video Files

BMP file extension

Bitmap Image File

Raster Image Files

CUE file extension

Cue Sheet File

Disk Image Files

DB file extension

Database File

Database Files

DEB file extension

Debian Software Package

Compressed Files

GZ file extension

Gnu Zipped Archive

Compressed Files

H file extension

C/C++/Objective-C Header File

Developer Files

HTML file extension

Hypertext Markup Language File

Web Files

IBOOKS file extension

Multi-Touch iBook

Data Files

KEY file extension

Keynote Presentation

Data Files

M3U file extension

Media Playlist File

Audio Files

SDF file extension

Standard Data File

Data Files

TTF file extension

TrueType Font

Font Files

VOB file extension

DVD Video Object File

Video Files