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

DDS file extension

DirectDraw Surface

Raster Image Files

DNG file extension

Digital Negative Image File

Camera Raw Files

DRV file extension

Device Driver

System Files

IBOOKS file extension

Multi-Touch iBook

Data Files

ICNS file extension

Mac OS X Icon Resource File

System Files

INDD file extension

Adobe InDesign Document

Layout Files

M4A file extension

MPEG-4 Audio File

Audio Files

MOBI file extension

Mobipocket eBook

eBook Files

OBJ file extension

Wavefront 3D Object File

3D Image Files

PY file extension

Python Script

Developer Files

RM file extension

Real Media File

Video Files

RPM file extension

Red Hat Package Manager File

Compressed Files

WPD file extension

WordPerfect Document

Text Files

WSF file extension

Windows Script File

Executable Files