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

C file extension

C/C++ Source Code File

Developer Files

CFG file extension

Configuration File

Settings Files

DOCX file extension

Microsoft Word Open XML Document

Text Files

DRV file extension

Device Driver

System Files

EPUB file extension

Open eBook File

eBook Files

GZ file extension

Gnu Zipped Archive

Compressed Files

IBOOKS file extension

Multi-Touch iBook

Data Files

ODT file extension

OpenDocument Text Document

Text Files

OTF file extension

OpenType Font

Font Files

PPS file extension

PowerPoint Slide Show

Data Files

PPT file extension

PowerPoint Presentation

Data Files

SLN file extension

Visual Studio Solution File

Developer Files

UUE file extension

Uuencoded File

Encoded Files

WPS file extension

Microsoft Works Word Processor Document

Text Files

3DM file extension

Rhino 3D Model

3D Image Files