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

CGI file extension

Common Gateway Interface Script

Executable Files

CLASS file extension

Java Class File

Developer Files

DEM file extension

Video Game Demo File

Game Files

GAM file extension

Saved Game File

Game Files

HTM file extension

Hypertext Markup Language File

Web Files

HTML file extension

Hypertext Markup Language File

Web Files

ICO file extension

Icon File

System Files

M4A file extension

MPEG-4 Audio File

Audio Files

PL file extension

Perl Script

Developer Files

PPTX file extension

PowerPoint Open XML Presentation

Data Files

ROM file extension

N64 Game ROM File

Game Files

WAV file extension

WAVE Audio File

Audio Files

WPD file extension

WordPerfect Document

Text Files

WSF file extension

Windows Script File

Executable Files

3G2 file extension

3GPP2 Multimedia File

Video Files