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

APP file extension

Mac OS X Application

Executable Files

CPP file extension

C++ Source Code File

Developer Files

DBF file extension

Database File

Database Files

DDS file extension

DirectDraw Surface

Raster Image Files

DMG file extension

Mac OS X Disk Image

Disk Image Files

GADGET file extension

Windows Gadget

Executable Files

ISO file extension

Disc Image File

Disk Image Files

LUA file extension

Lua Source File

Developer Files

MP3 file extension

MP3 Audio File

Audio Files

PCT file extension

Picture File

Layout Files

PDB file extension

Program Database

Database Files

PLUGIN file extension

Mac OS X Plug-in

Plugin Files

WMA file extension

Windows Media Audio File

Audio Files

XHTML file extension

Extensible Hypertext Markup Language File

Web Files

ZIP file extension

Zipped File

Compressed Files