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

ASX file extension

Microsoft ASF Redirector File

Video Files

CAB file extension

Windows Cabinet File

System Files

COM file extension

DOS Command File

Executable Files

DEM file extension

Video Game Demo File

Game Files

DOC file extension

Microsoft Word Document

Text Files

HQX file extension

BinHex 4.0 Encoded File

Encoded Files

IBOOKS file extension

Multi-Touch iBook

Data Files

JAVA file extension

Java Source Code File

Developer Files

JS file extension

JavaScript File

Web Files

M4V file extension

iTunes Video File

Video Files

MAX file extension

3ds Max Scene File

3D Image Files

MOBI file extension

Mobipocket eBook

eBook Files

PS file extension

PostScript File

Vector Image Files

ROM file extension

N64 Game ROM File

Game Files

TARGZ file extension

Compressed Tarball File

Compressed Files