TinkerCAD is a free online 3D modeling and circuit program that runs in a web browser. It was created by former Google engineers to make 3D modeling accessible to the general public. TinkerCAD Circuits allows users to simulate Arduino-based systems using blocks before testing them on real hardware. Components, circuits, and simulations can be built and programmed using a drag-and-drop interface or text code, with designs able to be shared publicly.