🧩 Sudoku Trainer (unique puzzles, hints & solver)

Play a freshly generated Sudoku with a guaranteed unique solution, get hints, or reveal the solution. Every puzzle is built on your device β€” nothing is fetched or sent.

Press β€œNew puzzle”.
Time: 0:00
Strategies (in order of usefulness)
1. Naked single β€” a cell with only one possible number left.
2. Hidden single β€” a number that can only go in one cell of a row, column or box.
3. Candidate elimination β€” cross out numbers that already appear in the same row, column or box.
4. Last resort for hard puzzles β€” the engine behind this tool uses backtracking with candidate shuffling: try a number, and if the search dead-ends, undo and try the next.

Guarantee: every puzzle is generated with exactly one solution β€” the generator removes cells one at a time and only keeps a removal if the solution stays unique.