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

AIF file extension

Audio Interchange File Format

Audio Files

CSV file extension

Comma Separated Values File

Data Files

CUR file extension

Windows Cursor

System Files

DLL file extension

Dynamic Link Library

System Files

DMP file extension

Windows Memory Dump

System Files

DOC file extension

Microsoft Word Document

Text Files

FNT file extension

Windows Font File

Font Files

JS file extension

JavaScript File

Web Files

JSP file extension

Java Server Page

Web Files

MOBI file extension

Mobipocket eBook

eBook Files

OTF file extension

OpenType Font

Font Files

PCT file extension

Picture File

Layout Files

PY file extension

Python Script

Developer Files

SH file extension

Bash Shell Script

Developer Files

3DM file extension

Rhino 3D Model

3D Image Files