TUIO is an open framework that defines a common protocol and API for tangible multitouch surfaces. The TUIO protocol allows the transmission of an abstract description of interactive surfaces, including touch events and tangible object states. This protocol encodes control data from a tracker application and sends it to any client application that is capable of decoding the protocol. There are a growing number of applications and TUIO client libraries for various programming environments. This combination of protocol and client implementations allows for the rapid development of table-based, tangible multitouch interfaces. TUIO has been designed mainly as an abstraction for interactive surfaces but is also used in many other related application areas.