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

AZW file extension

Amazon Kindle eBook File

eBook Files

BIN file extension

Binary Disc Image

Disk Image Files

C file extension

C/C++ Source Code File

Developer Files

CLASS file extension

Java Class File

Developer Files

CPP file extension

C++ Source Code File

Developer Files

CSS file extension

Cascading Style Sheet

Web Files

DOCX file extension

Microsoft Word Open XML Document

Text Files

GADGET file extension

Windows Gadget

Executable Files

HTML file extension

Hypertext Markup Language File

Web Files

MID file extension

MIDI File

Audio Files

MSI file extension

Windows Installer Package

Misc Files

TTF file extension

TrueType Font

Font Files

UUE file extension

Uuencoded File

Encoded Files

WPD file extension

WordPerfect Document

Text Files

XLSX file extension

Microsoft Excel Open XML Spreadsheet

Spreadsheet Files