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

BMP file extension

Bitmap Image File

Raster Image Files

CLASS file extension

Java Class File

Developer Files

CRX file extension

Chrome Extension

Plugin Files

DB file extension

Database File

Database Files

DOCX file extension

Microsoft Word Open XML Document

Text Files

GAM file extension

Saved Game File

Game Files

INI file extension

Windows Initialization File

Settings Files

M3U file extension

Media Playlist File

Audio Files

ODT file extension

OpenDocument Text Document

Text Files

PART file extension

Partially Downloaded File

Misc Files

PCT file extension

Picture File

Layout Files

PSD file extension

Adobe Photoshop Document

Raster Image Files

THM file extension

Thumbnail Image File

Raster Image Files

VOB file extension

DVD Video Object File

Video Files

3GP file extension

3GPP Multimedia File

Video Files