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

M3U file extension

Media Playlist File

Audio Files

SYS file extension

Windows System File

System Files

PART file extension

Partially Downloaded File

Misc Files

7Z file extension

7-Zip Compressed File

Compressed Files

IFF file extension

Interchange File Format

Audio Files

DXF file extension

Drawing Exchange Format File

CAD Files

HQX file extension

BinHex 4.0 Encoded File

Encoded Files

PY file extension

Python Script

Developer Files

ODT file extension

OpenDocument Text Document

Text Files

GPX file extension

GPS Exchange File

GIS Files

JS file extension

JavaScript File

Web Files

AIF file extension

Audio Interchange File Format

Audio Files

MID file extension

MIDI File

Audio Files

3DM file extension

Rhino 3D Model

3D Image Files

PDF file extension

Portable Document Format File

Layout Files