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

APK file extension

Android Package File

Executable Files

BAK file extension

Backup File

Backup Files

COM file extension

DOS Command File

Executable Files

CSR file extension

Certificate Signing Request File

Web Files

DEM file extension

Video Game Demo File

Game Files

DXF file extension

Drawing Exchange Format File

CAD Files

EXE file extension

Windows Executable File

Executable Files

INDD file extension

Adobe InDesign Document

Layout Files

KEY file extension

Keynote Presentation

Data Files

LUA file extension

Lua Source File

Developer Files

MSG file extension

Outlook Mail Message

Text Files

PNG file extension

Portable Network Graphic

Raster Image Files

SWF file extension

Shockwave Flash Movie

Video Files

TOAST file extension

Toast Disc Image

Disk Image Files

WSF file extension

Windows Script File

Executable Files