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

MP4 file extension

MPEG-4 Video File

Video Files

CLASS file extension

Java Class File

Developer Files

ICS file extension

iCalendar File

Misc Files

HQX file extension

BinHex 4.0 Encoded File

Encoded Files

RAR file extension

WinRAR Compressed Archive

Compressed Files

DMG file extension

Mac OS X Disk Image

Disk Image Files

AIF file extension

Audio Interchange File Format

Audio Files

3DM file extension

Rhino 3D Model

3D Image Files

GZ file extension

Gnu Zipped Archive

Compressed Files

NES file extension

Nintendo (NES) ROM File

Game Files

SVG file extension

Scalable Vector Graphics File

Vector Image Files

OBJ file extension

Wavefront 3D Object File

3D Image Files

DDS file extension

DirectDraw Surface

Raster Image Files

MID file extension

MIDI File

Audio Files

7Z file extension

7-Zip Compressed File

Compressed Files