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

APK file extension

Android Package File

Executable Files

ASPX file extension

Active Server Page Extended File

Web Files

BAK file extension

Backup File

Backup Files

BAT file extension

DOS Batch File

Executable Files

CS file extension

Visual C# Source Code File

Developer Files

DLL file extension

Dynamic Link Library

System Files

KEY file extension

Keynote Presentation

Data Files

MID file extension

MIDI File

Audio Files

OTF file extension

OpenType Font

Font Files

PS file extension

PostScript File

Vector Image Files

PY file extension

Python Script

Developer Files

ROM file extension

N64 Game ROM File

Game Files

SAV file extension

Saved Game

Game Files

SDF file extension

Standard Data File

Data Files

3DS file extension

3D Studio Scene

3D Image Files