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

APP file extension

Mac OS X Application

Executable Files

ASPX file extension

Active Server Page Extended File

Web Files

COM file extension

DOS Command File

Executable Files

CRDOWNLOAD file extension

Chrome Partially Downloaded File

Misc Files

CRX file extension

Chrome Extension

Plugin Files

DAT file extension

Data File

Data Files

GADGET file extension

Windows Gadget

Executable Files

JAVA file extension

Java Source Code File

Developer Files

JS file extension

JavaScript File

Web Files

MPA file extension

MPEG-2 Audio File

Audio Files

OBJ file extension

Wavefront 3D Object File

3D Image Files

ODT file extension

OpenDocument Text Document

Text Files

SAV file extension

Saved Game

Game Files

TORRENT file extension

BitTorrent File

Misc Files

VCD file extension

Virtual CD

Disk Image Files