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

AI file extension

Adobe Illustrator File

Vector Image Files

CBR file extension

Comic Book RAR Archive

Compressed Files

COM file extension

DOS Command File

Executable Files

CSS file extension

Cascading Style Sheet

Web Files

DOCX file extension

Microsoft Word Open XML Document

Text Files

HTM file extension

Hypertext Markup Language File

Web Files

JSP file extension

Java Server Page

Web Files

MIM file extension

Multi-Purpose Internet Mail Message File

Encoded Files

PCT file extension

Picture File

Layout Files

PHP file extension

PHP Source Code File

Web Files

PKG file extension

Mac OS X Installer Package

Compressed Files

PSD file extension

Adobe Photoshop Document

Raster Image Files

RM file extension

Real Media File

Video Files

SDF file extension

Standard Data File

Data Files

VB file extension

VBScript File

Executable Files