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

DLL file extension

Dynamic Link Library

System Files

GADGET file extension

Windows Gadget

Executable Files

KML file extension

Keyhole Markup Language File

GIS Files

KMZ file extension

Google Earth Placemark File

GIS Files

M4V file extension

iTunes Video File

Video Files

MDB file extension

Microsoft Access Database

Database Files

PAGES file extension

Pages Document

Text Files

ROM file extension

N64 Game ROM File

Game Files

RSS file extension

Rich Site Summary

Web Files

SITX file extension

StuffIt X Archive

Compressed Files

TIFF file extension

Tagged Image File Format

Raster Image Files

TMP file extension

Temporary File

Backup Files

VCF file extension

vCard File

Data Files

WAV file extension

WAVE Audio File

Audio Files