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

AIF file extension

Audio Interchange File Format

Audio Files

AZW file extension

Amazon Kindle eBook File

eBook Files

BAK file extension

Backup File

Backup Files

CFM file extension

ColdFusion Markup File

Web Files

CSR file extension

Certificate Signing Request File

Web Files

DEM file extension

Video Game Demo File

Game Files

DMG file extension

Mac OS X Disk Image

Disk Image Files

DOC# file extension

Microsoft Word Document

Text Files

FLV file extension

Flash Video File

Video Files

INI file extension

Windows Initialization File

Settings Files

JPG file extension

JPEG Image

Raster Image Files

OTF file extension

OpenType Font

Font Files

RAR file extension

WinRAR Compressed Archive

Compressed Files

WAV file extension

WAVE Audio File

Audio Files

WMA file extension

Windows Media Audio File

Audio Files