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

CPP file extension

C++ Source Code File

Developer Files

DEB file extension

Debian Software Package

Compressed Files

DOC# file extension

Microsoft Word Document

Text Files

DOCX file extension

Microsoft Word Open XML Document

Text Files

HTML file extension

Hypertext Markup Language File

Web Files

INDD file extension

Adobe InDesign Document

Layout Files

JAR file extension

Java Archive File

Executable Files

M file extension

Objective-C Implementation File

Developer Files

MDB file extension

Microsoft Access Database

Database Files

NES file extension

Nintendo (NES) ROM File

Game Files

PPTX file extension

PowerPoint Open XML Presentation

Data Files

TAR file extension

Consolidated Unix File Archive

Data Files

XHTML file extension

Extensible Hypertext Markup Language File

Web Files

ZIPX file extension

Extended Zip File

Compressed Files