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

CSV file extension

Comma Separated Values File

Data Files

DB file extension

Database File

Database Files

DEM file extension

Video Game Demo File

Game Files

DWG file extension

AutoCAD Drawing Database File

CAD Files

HQX file extension

BinHex 4.0 Encoded File

Encoded Files

JAVA file extension

Java Source Code File

Developer Files

M file extension

Objective-C Implementation File

Developer Files

MP4 file extension

MPEG-4 Video File

Video Files

OBJ file extension

Wavefront 3D Object File

3D Image Files

PIF file extension

Program Information File

Executable Files

SYS file extension

Windows System File

System Files

TIFF file extension

Tagged Image File Format

Raster Image Files

TOAST file extension

Toast Disc Image

Disk Image Files

WPD file extension

WordPerfect Document

Text Files

ZIPX file extension

Extended Zip File

Compressed Files