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

CLASS file extension

Java Class File

Developer Files

CPL file extension

Windows Control Panel Item

System Files

CS file extension

Visual C# Source Code File

Developer Files

FON file extension

Generic Font File

Font Files

HTM file extension

Hypertext Markup Language File

Web Files

IFF file extension

Interchange File Format

Audio Files

JAR file extension

Java Archive File

Executable Files

JPG file extension

JPEG Image

Raster Image Files

MAX file extension

3ds Max Scene File

3D Image Files

MSI file extension

Windows Installer Package

Misc Files

PY file extension

Python Script

Developer Files

RTF file extension

Rich Text Format File

Text Files

SYS file extension

Windows System File

System Files

VCD file extension

Virtual CD

Disk Image Files

VCF file extension

vCard File

Data Files