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

PCT file extension

Picture File

Layout Files

RTF file extension

Rich Text Format File

Text Files

IFF file extension

Interchange File Format

Audio Files

MPG file extension

MPEG Video File

Video Files

TIF file extension

Tagged Image File

Raster Image Files

PKG file extension

Mac OS X Installer Package

Compressed Files

XCODEPROJ file extension

Xcode Project

Developer Files

7Z file extension

7-Zip Compressed File

Compressed Files

CRX file extension

Chrome Extension

Plugin Files

MIM file extension

Multi-Purpose Internet Mail Message File

Encoded Files

CGI file extension

Common Gateway Interface Script

Executable Files

SRT file extension

SubRip Subtitle File

Video Files

FLV file extension

Flash Video File

Video Files

HQX file extension

BinHex 4.0 Encoded File

Encoded Files

MID file extension

MIDI File

Audio Files