How to Play Sudoku
Sudoku is a logic puzzle played on a 9×9 grid. The goal is simple: fill every row, every column, and every 3×3 box with the digits 1 through 9, without repeating any digit in a row, column, or box. You never need to guess — every well-made puzzle can be solved by reasoning alone. See also our Sudoku FAQ.
The three rules
- Each row must contain the digits 1–9 exactly once.
- Each column must contain the digits 1–9 exactly once.
- Each 3×3 box (outlined by thicker lines) must contain the digits 1–9 exactly once.
How to get started
Some cells are filled in when the puzzle begins — these are “given” numbers and cannot be changed. Your job is to work out what goes in the empty cells. A common approach:
- Look for rows, columns, or boxes that are almost complete — often only one digit fits in a remaining cell.
- Check which digits are already used in a cell’s row, column, and box to narrow the options.
- If you use pencil marks (small candidate numbers), cross off digits that are ruled out by the three rules above.
- When a cell can only take one digit, fill it in and use that new information on neighbouring cells.
Basic techniques
Naked single — an empty cell where only one digit is still possible after checking its row, column, and box.
Hidden single — within a row, column, or box, a digit can only go in one cell, even if that cell has other candidates too.
Harder puzzles require more advanced patterns (pairs, X-wing, and beyond). See our Sudoku techniques guide for longer explanations. Coaching hints on the play page name the next technique; on harder tiers, hints focus on the next logical deduction without giving away the whole board.
Playing on this site
- Daily puzzles — a fresh set of four puzzles every day: Easy, Medium, Hard, and Expert. Open Previous days to play any day from the last 90 days.
- No account needed — open the page and play. Your progress is saved in this browser automatically.
- Input — click a cell, then type 1–9 on your keyboard or use the on-screen number pad. Arrow keys move between cells. Backspace or Delete erases your entry or clears pencil marks.
- Notes — tap Notes to toggle pencil mode, then tap numbers to add or remove small candidates in a cell.
- Timer — a clock runs while you play so you can track how long a solve takes. It pauses when you finish or when the board locks after three mistakes.
- Mistakes — wrong entries turn red and count toward your mistake total (shown as 0/3). You can keep playing and fix them, or hit Reset to start the tier again.
- Hints — tap Hint for a coaching explanation of the next logical step. On singles, you can fill the cell in directly from the hint.
- Difficulty — Easy puzzles need only basic singles. Medium adds pairs and box-line reductions. Hard typically needs an X-wing. Expert goes deeper. The label reflects the hardest technique required, not just how many cells are blank.
Tips for faster solving
- Work systematically — scan all nine rows, then columns, then boxes, rather than jumping randomly.
- When you place a digit, immediately check what it eliminates in the same row, column, and box.
- On Medium and above, look for two cells in a unit that share the same two candidates — neither digit can appear elsewhere in that unit.
- If you get stuck, use a hint rather than guessing. Guessing often leads to contradictions later.
A note on difficulty
Not all Sudoku apps rate difficulty the same way. Some use blank-count alone, which is misleading — a puzzle with fewer givens is not always harder if it still yields to simple singles. Here, each tier is generated and checked so the label matches the technique you actually need. That takes longer to produce, but the label means something.