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

CAB file extension

Windows Cabinet File

System Files

DOCX file extension

Microsoft Word Open XML Document

Text Files

DTD file extension

Document Type Definition File

Developer Files

GADGET file extension

Windows Gadget

Executable Files

GBR file extension

Gerber File

Data Files

IFF file extension

Interchange File Format

Audio Files

KEY file extension

Keynote Presentation

Data Files

KML file extension

Keyhole Markup Language File

GIS Files

M3U file extension

Media Playlist File

Audio Files

OBJ file extension

Wavefront 3D Object File

3D Image Files

PDF file extension

Portable Document Format File

Layout Files

ROM file extension

N64 Game ROM File

Game Files

TGA file extension

Targa Graphic

Raster Image Files

XHTML file extension

Extensible Hypertext Markup Language File

Web Files

XML file extension

XML File

Data Files