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

DLL file extension

Dynamic Link Library

System Files

WMA file extension

Windows Media Audio File

Audio Files

SH file extension

Bash Shell Script

Developer Files

7Z file extension

7-Zip Compressed File

Compressed Files

DOC file extension

Microsoft Word Document

Text Files

RM file extension

Real Media File

Video Files

MDF file extension

Media Disc Image File

Disk Image Files

DEM file extension

Video Game Demo File

Game Files

WPS file extension

Microsoft Works Word Processor Document

Text Files

TOAST file extension

Toast Disc Image

Disk Image Files

CAB file extension

Windows Cabinet File

System Files

TIFF file extension

Tagged Image File Format

Raster Image Files

M3U file extension

Media Playlist File

Audio Files

PDF file extension

Portable Document Format File

Layout Files

AVI file extension

Audio Video Interleave File

Video Files