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

DXF file extension

Drawing Exchange Format File

CAD Files

GIF file extension

Graphical Interchange Format File

Raster Image Files

ICNS file extension

Mac OS X Icon Resource File

System Files

LNK file extension

Windows File Shortcut

System Files

M file extension

Objective-C Implementation File

Developer Files

M4A file extension

MPEG-4 Audio File

Audio Files

MOBI file extension

Mobipocket eBook

eBook Files

MSI file extension

Windows Installer Package

Misc Files

PDB file extension

Program Database

Database Files

PNG file extension

Portable Network Graphic

Raster Image Files

RAR file extension

WinRAR Compressed Archive

Compressed Files

RSS file extension

Rich Site Summary

Web Files

WAV file extension

WAVE Audio File

Audio Files

YUV file extension

YUV Encoded Image File

Raster Image Files