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

ASPX file extension

Active Server Page Extended File

Web Files

7Z file extension

7-Zip Compressed File

Compressed Files

SDF file extension

Standard Data File

Data Files

PS file extension

PostScript File

Vector Image Files

XCODEPROJ file extension

Xcode Project

Developer Files

VOB file extension

DVD Video Object File

Video Files

MPG file extension

MPEG Video File

Video Files

RA file extension

Real Audio File

Audio Files

DOC file extension

Microsoft Word Document

Text Files

CPP file extension

C++ Source Code File

Developer Files

KEY file extension

Keynote Presentation

Data Files

OTF file extension

OpenType Font

Font Files

PNG file extension

Portable Network Graphic

Raster Image Files

LNK file extension

Windows File Shortcut

System Files

3DM file extension

Rhino 3D Model

3D Image Files