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

ASX file extension

Microsoft ASF Redirector File

Video Files

CER file extension

Internet Security Certificate

Web Files

CRDOWNLOAD file extension

Chrome Partially Downloaded File

Misc Files

CSR file extension

Certificate Signing Request File

Web Files

DAT file extension

Data File

Data Files

DXF file extension

Drawing Exchange Format File

CAD Files

ICNS file extension

Mac OS X Icon Resource File

System Files

INI file extension

Windows Initialization File

Settings Files

MOBI file extension

Mobipocket eBook

eBook Files

MSI file extension

Windows Installer Package

Misc Files

PNG file extension

Portable Network Graphic

Raster Image Files

SLN file extension

Visual Studio Solution File

Developer Files

TORRENT file extension

BitTorrent File

Misc Files

3DM file extension

Rhino 3D Model

3D Image Files