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

CFG file extension

Configuration File

Settings Files

CRX file extension

Chrome Extension

Plugin Files

DOCX file extension

Microsoft Word Open XML Document

Text Files

DWG file extension

AutoCAD Drawing Database File

CAD Files

FLV file extension

Flash Video File

Video Files

FNT file extension

Windows Font File

Font Files

ICNS file extension

Mac OS X Icon Resource File

System Files

MDF file extension

Media Disc Image File

Disk Image Files

MPA file extension

MPEG-2 Audio File

Audio Files

PAGES file extension

Pages Document

Text Files

PY file extension

Python Script

Developer Files

RTF file extension

Rich Text Format File

Text Files

TOAST file extension

Toast Disc Image

Disk Image Files

WPD file extension

WordPerfect Document

Text Files

XHTML file extension

Extensible Hypertext Markup Language File

Web Files