MechaCanvas is a browser studio for building real robots. Pick from 41 official URDF models (24 humanoids, 16 arms, a quadruped) or import your own URDF/USD, pose joints in a 3D viewer, wire sensors and servos on a virtual breadboard, and program behaviors with blocks. The same behavior runs in the in-browser simulator and can stream over Web Serial to an ESP32 runtime or ROBOTIS/Feetech smart servos. No install, 8 languages.