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

XHTML file extension

Extensible Hypertext Markup Language File

Web Files

PPTX file extension

PowerPoint Open XML Presentation

Data Files

3DM file extension

Rhino 3D Model

3D Image Files

HQX file extension

BinHex 4.0 Encoded File

Encoded Files

ASP file extension

Active Server Page

Web Files

GAM file extension

Saved Game File

Game Files

7Z file extension

7-Zip Compressed File

Compressed Files

JS file extension

JavaScript File

Web Files

PPS file extension

PowerPoint Slide Show

Data Files

DWG file extension

AutoCAD Drawing Database File

CAD Files

PS file extension

PostScript File

Vector Image Files

MPG file extension

MPEG Video File

Video Files

CLASS file extension

Java Class File

Developer Files

M4V file extension

iTunes Video File

Video Files

KEY file extension

Keynote Presentation

Data Files