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

KML file extension

Keyhole Markup Language File

GIS Files

PIF file extension

Program Information File

Executable Files

VCD file extension

Virtual CD

Disk Image Files

CLASS file extension

Java Class File

Developer Files

JS file extension

JavaScript File

Web Files

7Z file extension

7-Zip Compressed File

Compressed Files

MDF file extension

Media Disc Image File

Disk Image Files

YUV file extension

YUV Encoded Image File

Raster Image Files

LNK file extension

Windows File Shortcut

System Files

APP file extension

Mac OS X Application

Executable Files

DB file extension

Database File

Database Files

PY file extension

Python Script

Developer Files

CSV file extension

Comma Separated Values File

Data Files

WSF file extension

Windows Script File

Executable Files

DOCX file extension

Microsoft Word Open XML Document

Text Files