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

ASX file extension

Microsoft ASF Redirector File

Video Files

BAT file extension

DOS Batch File

Executable Files

CSS file extension

Cascading Style Sheet

Web Files

DWG file extension

AutoCAD Drawing Database File

CAD Files

GED file extension

GEDCOM Genealogy Data File

Data Files

GIF file extension

Graphical Interchange Format File

Raster Image Files

HTM file extension

Hypertext Markup Language File

Web Files

KEYCHAIN file extension

Mac OS X Keychain File

Data Files

MID file extension

MIDI File

Audio Files

MIM file extension

Multi-Purpose Internet Mail Message File

Encoded Files

NES file extension

Nintendo (NES) ROM File

Game Files

OBJ file extension

Wavefront 3D Object File

3D Image Files

PS file extension

PostScript File

Vector Image Files

SITX file extension

StuffIt X Archive

Compressed Files

TORRENT file extension

BitTorrent File

Misc Files