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

ASP file extension

Active Server Page

Web Files

CER file extension

Internet Security Certificate

Web Files

COM file extension

DOS Command File

Executable Files

DEB file extension

Debian Software Package

Compressed Files

FON file extension

Generic Font File

Font Files

IBOOKS file extension

Multi-Touch iBook

Data Files

KEY file extension

Keynote Presentation

Data Files

MOBI file extension

Mobipocket eBook

eBook Files

NES file extension

Nintendo (NES) ROM File

Game Files

PPS file extension

PowerPoint Slide Show

Data Files

PPT file extension

PowerPoint Presentation

Data Files

RM file extension

Real Media File

Video Files

TORRENT file extension

BitTorrent File

Misc Files

VCD file extension

Virtual CD

Disk Image Files

3DM file extension

Rhino 3D Model

3D Image Files