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

BIN file extension

Binary Disc Image

Disk Image Files

CRX file extension

Chrome Extension

Plugin Files

DEB file extension

Debian Software Package

Compressed Files

ICNS file extension

Mac OS X Icon Resource File

System Files

INDD file extension

Adobe InDesign Document

Layout Files

JAVA file extension

Java Source Code File

Developer Files

KEY file extension

Keynote Presentation

Data Files

M4V file extension

iTunes Video File

Video Files

MSG file extension

Outlook Mail Message

Text Files

PDF file extension

Portable Document Format File

Layout Files

PY file extension

Python Script

Developer Files

TAR file extension

Consolidated Unix File Archive

Data Files

TARGZ file extension

Compressed Tarball File

Compressed Files

XML file extension

XML File

Data Files

3GP file extension

3GPP Multimedia File

Video Files