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

CER file extension

Internet Security Certificate

Web Files

CUE file extension

Cue Sheet File

Disk Image Files

DESKTHEMEPACK file extension

Windows 8 Desktop Theme Pack File

System Files

DNG file extension

Digital Negative Image File

Camera Raw Files

DWG file extension

AutoCAD Drawing Database File

CAD Files

IBOOKS file extension

Multi-Touch iBook

Data Files

IFF file extension

Interchange File Format

Audio Files

KML file extension

Keyhole Markup Language File

GIS Files

MIM file extension

Multi-Purpose Internet Mail Message File

Encoded Files

MP3 file extension

MP3 Audio File

Audio Files

PART file extension

Partially Downloaded File

Misc Files

PNG file extension

Portable Network Graphic

Raster Image Files

PSD file extension

Adobe Photoshop Document

Raster Image Files

TIFF file extension

Tagged Image File Format

Raster Image Files

XCODEPROJ file extension

Xcode Project

Developer Files