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

DMG file extension

Mac OS X Disk Image

Disk Image Files

DWG file extension

AutoCAD Drawing Database File

CAD Files

JS file extension

JavaScript File

Web Files

LOG file extension

Log File

Text Files

MSG file extension

Outlook Mail Message

Text Files

PDF file extension

Portable Document Format File

Layout Files

PLUGIN file extension

Mac OS X Plug-in

Plugin Files

RSS file extension

Rich Site Summary

Web Files

RTF file extension

Rich Text Format File

Text Files

SH file extension

Bash Shell Script

Developer Files

SVG file extension

Scalable Vector Graphics File

Vector Image Files

TOAST file extension

Toast Disc Image

Disk Image Files

TORRENT file extension

BitTorrent File

Misc Files

TXT file extension

Plain Text File

Text Files