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

PDF file extension

Portable Document Format File

Layout Files

RA file extension

Real Audio File

Audio Files

APP file extension

Mac OS X Application

Executable Files

M3U file extension

Media Playlist File

Audio Files

IFF file extension

Interchange File Format

Audio Files

DLL file extension

Dynamic Link Library

System Files

VOB file extension

DVD Video Object File

Video Files

PHP file extension

PHP Source Code File

Web Files

ICO file extension

Icon File

System Files

HTML file extension

Hypertext Markup Language File

Web Files

MP3 file extension

MP3 Audio File

Audio Files

CS file extension

Visual C# Source Code File

Developer Files

7Z file extension

7-Zip Compressed File

Compressed Files

WPD file extension

WordPerfect Document

Text Files

TIF file extension

Tagged Image File

Raster Image Files