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

INDD file extension

Adobe InDesign Document

Layout Files

7Z file extension

7-Zip Compressed File

Compressed Files

XML file extension

XML File

Data Files

FLV file extension

Flash Video File

Video Files

TOAST file extension

Toast Disc Image

Disk Image Files

DNG file extension

Digital Negative Image File

Camera Raw Files

TXT file extension

Plain Text File

Text Files

RSS file extension

Rich Site Summary

Web Files

XCODEPROJ file extension

Xcode Project

Developer Files

C file extension

C/C++ Source Code File

Developer Files

MSG file extension

Outlook Mail Message

Text Files

THM file extension

Thumbnail Image File

Raster Image Files

DEM file extension

Video Game Demo File

Game Files

PDB file extension

Program Database

Database Files

JS file extension

JavaScript File

Web Files