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

AZW file extension

Amazon Kindle eBook File

eBook Files

BMP file extension

Bitmap Image File

Raster Image Files

C file extension

C/C++ Source Code File

Developer Files

CAB file extension

Windows Cabinet File

System Files

CFG file extension

Configuration File

Settings Files

DB file extension

Database File

Database Files

GAM file extension

Saved Game File

Game Files

INDD file extension

Adobe InDesign Document

Layout Files

ISO file extension

Disc Image File

Disk Image Files

LNK file extension

Windows File Shortcut

System Files

LOG file extension

Log File

Text Files

MP4 file extension

MPEG-4 Video File

Video Files

PLUGIN file extension

Mac OS X Plug-in

Plugin Files

SYS file extension

Windows System File

System Files