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

ASF file extension

Advanced Systems Format File

Video Files

BIN file extension

Binary Disc Image

Disk Image Files

CFG file extension

Configuration File

Settings Files

DESKTHEMEPACK file extension

Windows 8 Desktop Theme Pack File

System Files

DLL file extension

Dynamic Link Library

System Files

DNG file extension

Digital Negative Image File

Camera Raw Files

HTM file extension

Hypertext Markup Language File

Web Files

M file extension

Objective-C Implementation File

Developer Files

PHP file extension

PHP Source Code File

Web Files

TAX2012 file extension

TurboTax 2012 Tax Return

Data Files

VB file extension

VBScript File

Executable Files

VCF file extension

vCard File

Data Files

XCODEPROJ file extension

Xcode Project

Developer Files

ZIPX file extension

Extended Zip File

Compressed Files

3DS file extension

3D Studio Scene

3D Image Files