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

AVI file extension

Audio Video Interleave File

Video Files

CAB file extension

Windows Cabinet File

System Files

CSR file extension

Certificate Signing Request File

Web Files

DAT file extension

Data File

Data Files

DESKTHEMEPACK file extension

Windows 8 Desktop Theme Pack File

System Files

DMP file extension

Windows Memory Dump

System Files

DOC# file extension

Microsoft Word Document

Text Files

INDD file extension

Adobe InDesign Document

Layout Files

INI file extension

Windows Initialization File

Settings Files

JS file extension

JavaScript File

Web Files

MID file extension

MIDI File

Audio Files

NES file extension

Nintendo (NES) ROM File

Game Files

PRF file extension

Outlook Profile File

Settings Files

SAV file extension

Saved Game

Game Files

XLR file extension

Works Spreadsheet

Spreadsheet Files