A runtime environment created for Mac OS X by Arlo Rose and Perry Clarke. Konfabulator runs "widgets" which are Mac OS X bundles containing a .kon file and any necessary assets. Assets can be almost anything, including images, sounds, scripts, or even standalone executables.

Widgets are programmed web-page style using a combination of XML and Javascript. The XML contains the data abstraction for the UI while Javascript provides the top-level scripting of that UI. The Javascript language has been extended with specific builtin functions for executing Applescripts, running shell commands, and various other useful tasks.

The great power of Konfabulator is hidden beneath its simplicity. The major work of developing a widget is in designing the graphics for the UI, which can be as customized as you can imagine. There is a strong emphasis on using PNG files due to their support for alpha blending. Most widgets use transparency in one form or another.

Widgets are by nature completely Open Source. The .kon files are plain text, readable by anyone curious enough to look. This is both a blessing and a bane to Konfabulator, as there are likely to be thousands of cheap knock-offs of earlier widgets.

Konfabulator exploded on the scene in February of 2003 and within two weeks there were over 150 widgets submitted to the Konfabulator site. Predictably most of them have been half-hearted derivative works such as floating desktop clocks and RSS feed viewers.

Adding it all up Konfabulator is a very cool idea well-implemented by its authors. Arlo Rose has an extensive background as a Mac developer, having contributed his tasteful design sense and creative spark in collaboration with Greg Landweber to create the Mac OS 8/9 interface customizer Kaleidoscope, which set the bar for interface customization tools.Konfabulator continues that tradition, only moreso.