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

BAK file extension

Backup File

Backup Files

CUE file extension

Cue Sheet File

Disk Image Files

DMP file extension

Windows Memory Dump

System Files

DOC file extension

Microsoft Word Document

Text Files

EPUB file extension

Open eBook File

eBook Files

INDD file extension

Adobe InDesign Document

Layout Files

M4A file extension

MPEG-4 Audio File

Audio Files

MSG file extension

Outlook Mail Message

Text Files

NES file extension

Nintendo (NES) ROM File

Game Files

RA file extension

Real Audio File

Audio Files

TAX2012 file extension

TurboTax 2012 Tax Return

Data Files

TXT file extension

Plain Text File

Text Files

VCF file extension

vCard File

Data Files

3DM file extension

Rhino 3D Model

3D Image Files

3G2 file extension

3GPP2 Multimedia File

Video Files