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

BMP file extension

Bitmap Image File

Raster Image Files

CAB file extension

Windows Cabinet File

System Files

CPP file extension

C++ Source Code File

Developer Files

DESKTHEMEPACK file extension

Windows 8 Desktop Theme Pack File

System Files

EXE file extension

Windows Executable File

Executable Files

GADGET file extension

Windows Gadget

Executable Files

INDD file extension

Adobe InDesign Document

Layout Files

JSP file extension

Java Server Page

Web Files

KML file extension

Keyhole Markup Language File

GIS Files

PAGES file extension

Pages Document

Text Files

RSS file extension

Rich Site Summary

Web Files

XML file extension

XML File

Data Files

ZIP file extension

Zipped File

Compressed Files

3DM file extension

Rhino 3D Model

3D Image Files