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

INDD file extension

Adobe InDesign Document

Layout Files

DMP file extension

Windows Memory Dump

System Files

HTML file extension

Hypertext Markup Language File

Web Files

ICO file extension

Icon File

System Files

WMV file extension

Windows Media Video File

Video Files

JAVA file extension

Java Source Code File

Developer Files

MID file extension

MIDI File

Audio Files

SITX file extension

StuffIt X Archive

Compressed Files

ASPX file extension

Active Server Page Extended File

Web Files

RA file extension

Real Audio File

Audio Files

WSF file extension

Windows Script File

Executable Files

CS file extension

Visual C# Source Code File

Developer Files

7Z file extension

7-Zip Compressed File

Compressed Files

PPTX file extension

PowerPoint Open XML Presentation

Data Files

DNG file extension

Digital Negative Image File

Camera Raw Files