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

CBR file extension

Comic Book RAR Archive

Compressed Files

CFM file extension

ColdFusion Markup File

Web Files

CSS file extension

Cascading Style Sheet

Web Files

DMP file extension

Windows Memory Dump

System Files

DNG file extension

Digital Negative Image File

Camera Raw Files

DOCX file extension

Microsoft Word Open XML Document

Text Files

DTD file extension

Document Type Definition File

Developer Files

HQX file extension

BinHex 4.0 Encoded File

Encoded Files

OTF file extension

OpenType Font

Font Files

PKG file extension

Mac OS X Installer Package

Compressed Files

RA file extension

Real Audio File

Audio Files

SWF file extension

Shockwave Flash Movie

Video Files

XML file extension

XML File

Data Files

ZIP file extension

Zipped File

Compressed Files

3DS file extension

3D Studio Scene

3D Image Files