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

BMP file extension

Bitmap Image File

Raster Image Files

CPL file extension

Windows Control Panel Item

System Files

DAT file extension

Data File

Data Files

EPUB file extension

Open eBook File

eBook Files

GADGET file extension

Windows Gadget

Executable Files

HQX file extension

BinHex 4.0 Encoded File

Encoded Files

JS file extension

JavaScript File

Web Files

KEYCHAIN file extension

Mac OS X Keychain File

Data Files

PCT file extension

Picture File

Layout Files

RA file extension

Real Audio File

Audio Files

ROM file extension

N64 Game ROM File

Game Files

SITX file extension

StuffIt X Archive

Compressed Files

TIFF file extension

Tagged Image File Format

Raster Image Files

TXT file extension

Plain Text File

Text Files

WPD file extension

WordPerfect Document

Text Files