reacTIVision is a computer vision framework for the fast and robust tracking of fiducial markers attached to physical objects, as well as for multi-touch finger tracking. It was mainly designed as a toolkit for the rapid development of table-based tangible user interfaces and interactive multi-touch surfaces such as the reacTable. Client application examples are available for various programming environments such as C++, Java, C#, Processing, PureData, Max/MSP, and Quartz Composer.