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

CLASS file extension

Java Class File

Developer Files

CUE file extension

Cue Sheet File

Disk Image Files

DDS file extension

DirectDraw Surface

Raster Image Files

DLL file extension

Dynamic Link Library

System Files

M file extension

Objective-C Implementation File

Developer Files

M4V file extension

iTunes Video File

Video Files

MPA file extension

MPEG-2 Audio File

Audio Files

PHP file extension

PHP Source Code File

Web Files

PS file extension

PostScript File

Vector Image Files

SITX file extension

StuffIt X Archive

Compressed Files

SWF file extension

Shockwave Flash Movie

Video Files

TEX file extension

LaTeX Source Document

Text Files

VB file extension

VBScript File

Executable Files

VCF file extension

vCard File

Data Files

XLSX file extension

Microsoft Excel Open XML Spreadsheet

Spreadsheet Files