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How to play Sudoku
Rules
- Fill the 9×9 grid so every row, column, and 3×3 box contains the digits 1–9 exactly once.
- Some numbers are given at the start — those cells cannot be changed.
- There is only one valid solution for each puzzle.
Difficulty levels
Easy — more givens and simpler logical steps. Medium — fewer givens; you may need scanning and candidate notes. Hard — sparse grid; expect deeper patterns and patience.
Our puzzles are pre-rated and stored in the database; the same difficulty always draws from that tier’s pool.
Basic tactics
- Full house — if eight digits appear in a row, column, or box, the empty cell is the missing digit.
- Naked single — a cell has only one candidate left after eliminating digits that already appear in its row, column, and box.
- Scanning — place a digit in a box by seeing where it can’t go in intersecting rows/columns.
Interactive “technique tips” after mistakes may be added later; for now, use Notes (signed-in) to pencil in candidates.
Daily puzzle
From the home page, open Today’s puzzle for each difficulty — everyone gets the same grid for that day (picked deterministically from our catalog).