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

3DM file extension

Rhino 3D Model

3D Image Files

GADGET file extension

Windows Gadget

Executable Files

JS file extension

JavaScript File

Web Files

TXT file extension

Plain Text File

Text Files

DRV file extension

Device Driver

System Files

SLN file extension

Visual Studio Solution File

Developer Files

MOV file extension

Apple QuickTime Movie

Video Files

CAB file extension

Windows Cabinet File

System Files

XHTML file extension

Extensible Hypertext Markup Language File

Web Files

7Z file extension

7-Zip Compressed File

Compressed Files

DOC# file extension

Microsoft Word Document

Text Files

IFF file extension

Interchange File Format

Audio Files

TTF file extension

TrueType Font

Font Files

DESKTHEMEPACK file extension

Windows 8 Desktop Theme Pack File

System Files

IBOOKS file extension

Multi-Touch iBook

Data Files