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

CFG file extension

Configuration File

Settings Files

CLASS file extension

Java Class File

Developer Files

DTD file extension

Document Type Definition File

Developer Files

GIF file extension

Graphical Interchange Format File

Raster Image Files

MOV file extension

Apple QuickTime Movie

Video Files

MPA file extension

MPEG-2 Audio File

Audio Files

MSG file extension

Outlook Mail Message

Text Files

OBJ file extension

Wavefront 3D Object File

3D Image Files

RSS file extension

Rich Site Summary

Web Files

TIF file extension

Tagged Image File

Raster Image Files

VB file extension

VBScript File

Executable Files

YUV file extension

YUV Encoded Image File

Raster Image Files

3DM file extension

Rhino 3D Model

3D Image Files

3G2 file extension

3GPP2 Multimedia File

Video Files