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

ASPX file extension

Active Server Page Extended File

Web Files

BMP file extension

Bitmap Image File

Raster Image Files

CFG file extension

Configuration File

Settings Files

CS file extension

Visual C# Source Code File

Developer Files

FLA file extension

Adobe Flash Animation

Developer Files

HQX file extension

BinHex 4.0 Encoded File

Encoded Files

IBOOKS file extension

Multi-Touch iBook

Data Files

JAR file extension

Java Archive File

Executable Files

JAVA file extension

Java Source Code File

Developer Files

M4A file extension

MPEG-4 Audio File

Audio Files

PDF file extension

Portable Document Format File

Layout Files

PIF file extension

Program Information File

Executable Files

SAV file extension

Saved Game

Game Files

WPS file extension

Microsoft Works Word Processor Document

Text Files

3GP file extension

3GPP Multimedia File

Video Files