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

BMP file extension

Bitmap Image File

Raster Image Files

CGI file extension

Common Gateway Interface Script

Executable Files

CS file extension

Visual C# Source Code File

Developer Files

FLA file extension

Adobe Flash Animation

Developer Files

ICS file extension

iCalendar File

Misc Files

IFF file extension

Interchange File Format

Audio Files

JSP file extension

Java Server Page

Web Files

MAX file extension

3ds Max Scene File

3D Image Files

MP4 file extension

MPEG-4 Video File

Video Files

MSG file extension

Outlook Mail Message

Text Files

OTF file extension

OpenType Font

Font Files

PCT file extension

Picture File

Layout Files

PKG file extension

Mac OS X Installer Package

Compressed Files

PPS file extension

PowerPoint Slide Show

Data Files

SWF file extension

Shockwave Flash Movie

Video Files