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

BIN file extension

Binary Disc Image

Disk Image Files

CER file extension

Internet Security Certificate

Web Files

DOC# file extension

Microsoft Word Document

Text Files

DTD file extension

Document Type Definition File

Developer Files

GIF file extension

Graphical Interchange Format File

Raster Image Files

GPX file extension

GPS Exchange File

GIS Files

HQX file extension

BinHex 4.0 Encoded File

Encoded Files

ICO file extension

Icon File

System Files

INI file extension

Windows Initialization File

Settings Files

JAR file extension

Java Archive File

Executable Files

M4A file extension

MPEG-4 Audio File

Audio Files

M4V file extension

iTunes Video File

Video Files

RTF file extension

Rich Text Format File

Text Files

3DS file extension

3D Studio Scene

3D Image Files