Sudoku
How to play Sudoku
Sudoku is a logic puzzle on a 9×9 grid split into nine 3×3 boxes. Some squares start filled in with given numbers. Your job is to fill every empty square so that each row, each column and each 3×3 box contains the digits 1 to 9 exactly once — no repeats anywhere. There is no arithmetic; it is pure deduction, and every puzzle here has exactly one correct solution.
Select a square and type a number, or tap a cell then a number on the pad. Turn on Notes to pencil in the small candidate numbers you are still weighing up; placing a real number automatically clears that candidate from the rest of its row, column and box.
Beginner tactics that always work
- Hunt for forced squares. Scan each row, column and box for a digit that can go in only one remaining square — a “hidden single.” These are the backbone of every solve.
- Pencil in candidates. When a square has only one possible number left (a “naked single”), fill it. Notes make these jump out.
- Work the fullest units first. Rows, columns and boxes that already have the most numbers are the easiest to finish and unlock the rest.
- Never guess on easy or medium. Every puzzle up to hard can be solved by logic alone — if you are stuck, you have missed a single somewhere.
Four difficulties
Easy puzzles can be finished with single-candidate logic alone. Medium and hard ask for candidate elimination and pairs. Expert puzzles start from as few as 26 given numbers and reward patient, notes-driven deduction. Your best time for each level is saved on your device, and your current game resumes if you close the tab. This is duplixo’s own generator — free, no sign-up, and no ads on top of the board.