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

VB file extension

VBScript File

Executable Files

7Z file extension

7-Zip Compressed File

Compressed Files

MP3 file extension

MP3 Audio File

Audio Files

CS file extension

Visual C# Source Code File

Developer Files

XLSX file extension

Microsoft Excel Open XML Spreadsheet

Spreadsheet Files

YUV file extension

YUV Encoded Image File

Raster Image Files

DMG file extension

Mac OS X Disk Image

Disk Image Files

MOV file extension

Apple QuickTime Movie

Video Files

BMP file extension

Bitmap Image File

Raster Image Files

SQL file extension

Structured Query Language Data File

Database Files

CFM file extension

ColdFusion Markup File

Web Files

WMA file extension

Windows Media Audio File

Audio Files

DLL file extension

Dynamic Link Library

System Files

PNG file extension

Portable Network Graphic

Raster Image Files

VOB file extension

DVD Video Object File

Video Files