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

DEB file extension

Debian Software Package

Compressed Files

DLL file extension

Dynamic Link Library

System Files

DOC file extension

Microsoft Word Document

Text Files

DXF file extension

Drawing Exchange Format File

CAD Files

FLA file extension

Adobe Flash Animation

Developer Files

GED file extension

GEDCOM Genealogy Data File

Data Files

HTML file extension

Hypertext Markup Language File

Web Files

ICO file extension

Icon File

System Files

KEYCHAIN file extension

Mac OS X Keychain File

Data Files

NES file extension

Nintendo (NES) ROM File

Game Files

PSPIMAGE file extension

PaintShop Pro Image

Raster Image Files

RM file extension

Real Media File

Video Files

TORRENT file extension

BitTorrent File

Misc Files

XCODEPROJ file extension

Xcode Project

Developer Files

XLSX file extension

Microsoft Excel Open XML Spreadsheet

Spreadsheet Files