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

CFM file extension

ColdFusion Markup File

Web Files

DOC# file extension

Microsoft Word Document

Text Files

DRV file extension

Device Driver

System Files

DXF file extension

Drawing Exchange Format File

CAD Files

HQX file extension

BinHex 4.0 Encoded File

Encoded Files

HTM file extension

Hypertext Markup Language File

Web Files

INDD file extension

Adobe InDesign Document

Layout Files

JPG file extension

JPEG Image

Raster Image Files

JS file extension

JavaScript File

Web Files

MOBI file extension

Mobipocket eBook

eBook Files

PKG file extension

Mac OS X Installer Package

Compressed Files

PRF file extension

Outlook Profile File

Settings Files

RAR file extension

WinRAR Compressed Archive

Compressed Files

RTF file extension

Rich Text Format File

Text Files

UUE file extension

Uuencoded File

Encoded Files