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

AI file extension

Adobe Illustrator File

Vector Image Files

BAK file extension

Backup File

Backup Files

BMP file extension

Bitmap Image File

Raster Image Files

CGI file extension

Common Gateway Interface Script

Executable Files

CPP file extension

C++ Source Code File

Developer Files

IFF file extension

Interchange File Format

Audio Files

INI file extension

Windows Initialization File

Settings Files

LUA file extension

Lua Source File

Developer Files

M3U file extension

Media Playlist File

Audio Files

MDF file extension

Media Disc Image File

Disk Image Files

PKG file extension

Mac OS X Installer Package

Compressed Files

PY file extension

Python Script

Developer Files

RSS file extension

Rich Site Summary

Web Files

TIF file extension

Tagged Image File

Raster Image Files

VCF file extension

vCard File

Data Files