Click here if you get a message indicating that the Java applet can not be started. 
This is the Sudoku 12x12 Horizontal. The rectangles can also be vertical. Rules:

The solver will always find a solution if it exists. If you press 'Solve', the solver will indicate that there is no solution, one solution, or more than one solution.
©2011, 2014 Renze de Waal.