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

COM file extension

DOS Command File

Executable Files

DNG file extension

Digital Negative Image File

Camera Raw Files

GIF file extension

Graphical Interchange Format File

Raster Image Files

KEY file extension

Keynote Presentation

Data Files

M file extension

Objective-C Implementation File

Developer Files

MID file extension

MIDI File

Audio Files

OBJ file extension

Wavefront 3D Object File

3D Image Files

PLUGIN file extension

Mac OS X Plug-in

Plugin Files

PPTX file extension

PowerPoint Open XML Presentation

Data Files

RSS file extension

Rich Site Summary

Web Files

SDF file extension

Standard Data File

Data Files

SWF file extension

Shockwave Flash Movie

Video Files

THM file extension

Thumbnail Image File

Raster Image Files

UUE file extension

Uuencoded File

Encoded Files

3DS file extension

3D Studio Scene

3D Image Files