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

BAT file extension

DOS Batch File

Executable Files

CPL file extension

Windows Control Panel Item

System Files

CPP file extension

C++ Source Code File

Developer Files

CSR file extension

Certificate Signing Request File

Web Files

CSV file extension

Comma Separated Values File

Data Files

DLL file extension

Dynamic Link Library

System Files

DWG file extension

AutoCAD Drawing Database File

CAD Files

JAR file extension

Java Archive File

Executable Files

JAVA file extension

Java Source Code File

Developer Files

JS file extension

JavaScript File

Web Files

OBJ file extension

Wavefront 3D Object File

3D Image Files

PL file extension

Perl Script

Developer Files

SAV file extension

Saved Game

Game Files

TOAST file extension

Toast Disc Image

Disk Image Files

3DS file extension

3D Studio Scene

3D Image Files