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

CER file extension

Internet Security Certificate

Web Files

DAT file extension

Data File

Data Files

DBF file extension

Database File

Database Files

DLL file extension

Dynamic Link Library

System Files

DOCX file extension

Microsoft Word Open XML Document

Text Files

DRV file extension

Device Driver

System Files

GPX file extension

GPS Exchange File

GIS Files

HQX file extension

BinHex 4.0 Encoded File

Encoded Files

JS file extension

JavaScript File

Web Files

JSP file extension

Java Server Page

Web Files

LUA file extension

Lua Source File

Developer Files

M4V file extension

iTunes Video File

Video Files

SDF file extension

Standard Data File

Data Files

SVG file extension

Scalable Vector Graphics File

Vector Image Files

XLSX file extension

Microsoft Excel Open XML Spreadsheet

Spreadsheet Files