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

DDS file extension

DirectDraw Surface

Raster Image Files

DEB file extension

Debian Software Package

Compressed Files

GADGET file extension

Windows Gadget

Executable Files

ISO file extension

Disc Image File

Disk Image Files

KEY file extension

Keynote Presentation

Data Files

KML file extension

Keyhole Markup Language File

GIS Files

MP4 file extension

MPEG-4 Video File

Video Files

MSI file extension

Windows Installer Package

Misc Files

PKG file extension

Mac OS X Installer Package

Compressed Files

PSD file extension

Adobe Photoshop Document

Raster Image Files

RPM file extension

Red Hat Package Manager File

Compressed Files

SVG file extension

Scalable Vector Graphics File

Vector Image Files

SYS file extension

Windows System File

System Files

TXT file extension

Plain Text File

Text Files

3G2 file extension

3GPP2 Multimedia File

Video Files