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

ZIPX file extension

Extended Zip File

Compressed Files

BAK file extension

Backup File

Backup Files

DEB file extension

Debian Software Package

Compressed Files

DB file extension

Database File

Database Files

RSS file extension

Rich Site Summary

Web Files

KMZ file extension

Google Earth Placemark File

GIS Files

MSG file extension

Outlook Mail Message

Text Files

CLASS file extension

Java Class File

Developer Files

CSS file extension

Cascading Style Sheet

Web Files

CRX file extension

Chrome Extension

Plugin Files

DOCX file extension

Microsoft Word Open XML Document

Text Files

3DM file extension

Rhino 3D Model

3D Image Files

MDB file extension

Microsoft Access Database

Database Files

7Z file extension

7-Zip Compressed File

Compressed Files

VCF file extension

vCard File

Data Files