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

APP file extension

Mac OS X Application

Executable 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

DOC file extension

Microsoft Word Document

Text Files

INDD file extension

Adobe InDesign Document

Layout Files

MDF file extension

Media Disc Image File

Disk Image Files

MID file extension

MIDI File

Audio Files

MIM file extension

Multi-Purpose Internet Mail Message File

Encoded Files

NES file extension

Nintendo (NES) ROM File

Game Files

PRF file extension

Outlook Profile File

Settings Files

RA file extension

Real Audio File

Audio Files

RAR file extension

WinRAR Compressed Archive

Compressed Files

RTF file extension

Rich Text Format File

Text Files