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

C file extension

C/C++ Source Code File

Developer Files

COM file extension

DOS Command File

Executable Files

DBF file extension

Database File

Database Files

DOCX file extension

Microsoft Word Open XML Document

Text Files

GAM file extension

Saved Game File

Game Files

HQX file extension

BinHex 4.0 Encoded File

Encoded Files

KEY file extension

Keynote Presentation

Data Files

MP3 file extension

MP3 Audio File

Audio Files

MP4 file extension

MPEG-4 Video File

Video Files

MSI file extension

Windows Installer Package

Misc Files

RM file extension

Real Media File

Video Files

SYS file extension

Windows System File

System Files

TIF file extension

Tagged Image File

Raster Image Files

VCXPROJ file extension

Visual C++ Project

Developer Files

YUV file extension

YUV Encoded Image File

Raster Image Files