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

CPL file extension

Windows Control Panel Item

System Files

CSV file extension

Comma Separated Values File

Data Files

DOCX file extension

Microsoft Word Open XML Document

Text Files

LUA file extension

Lua Source File

Developer Files

MP3 file extension

MP3 Audio File

Audio Files

MPG file extension

MPEG Video File

Video Files

PKG file extension

Mac OS X Installer Package

Compressed Files

PPT file extension

PowerPoint Presentation

Data Files

PSPIMAGE file extension

PaintShop Pro Image

Raster Image Files

SAV file extension

Saved Game

Game Files

TOAST file extension

Toast Disc Image

Disk Image Files

VCXPROJ file extension

Visual C++ Project

Developer Files

WPS file extension

Microsoft Works Word Processor Document

Text Files

3DS file extension

3D Studio Scene

3D Image Files