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

AIF file extension

Audio Interchange File Format

Audio Files

AVI file extension

Audio Video Interleave File

Video Files

CFM file extension

ColdFusion Markup File

Web Files

CSV file extension

Comma Separated Values File

Data Files

DLL file extension

Dynamic Link Library

System Files

DTD file extension

Document Type Definition File

Developer Files

EXE file extension

Windows Executable File

Executable Files

JAVA file extension

Java Source Code File

Developer Files

JS file extension

JavaScript File

Web Files

KEY file extension

Keynote Presentation

Data Files

MDF file extension

Media Disc Image File

Disk Image Files

MPG file extension

MPEG Video File

Video Files

PPS file extension

PowerPoint Slide Show

Data Files

RTF file extension

Rich Text Format File

Text Files

WPD file extension

WordPerfect Document

Text Files