Who this level is for
Diabolical is the strongest SudokuIQ level, intended for advanced solvers comfortable with dense candidate grids.
SudokuIQ puzzle
Play Diabolical Sudoku online
Solve a free diabolical Sudoku with notes, smart hints, coaching and local progress. Each board is generated from a valid solved grid and checked for a unique solution.
Logic you will use
Expect layered eliminations involving locked candidates, pairs or triples, and advanced line patterns.
How to practise
Treat every elimination as a proof. If a move cannot be explained by a row, column, box or candidate pattern, do not enter it.
What makes Diabolical different from Expert?
It generally offers fewer easy openings and requires more deductions that eliminate candidates before a number can be placed.
Can Coach explain advanced moves?
Coach is designed to identify a valid next step and show its focus. Academy coverage will continue expanding for advanced named patterns.