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

CS file extension

Visual C# Source Code File

Developer Files

CSV file extension

Comma Separated Values File

Data Files

DBF file extension

Database File

Database Files

DOCX file extension

Microsoft Word Open XML Document

Text Files

GIF file extension

Graphical Interchange Format File

Raster Image Files

GPX file extension

GPS Exchange File

GIS Files

HTML file extension

Hypertext Markup Language File

Web Files

ICO file extension

Icon File

System Files

INI file extension

Windows Initialization File

Settings Files

JS file extension

JavaScript File

Web Files

M4V file extension

iTunes Video File

Video Files

TAR file extension

Consolidated Unix File Archive

Data Files

TARGZ file extension

Compressed Tarball File

Compressed Files

TOAST file extension

Toast Disc Image

Disk Image Files

XLSX file extension

Microsoft Excel Open XML Spreadsheet

Spreadsheet Files