About this game
Sudoku is a logic puzzle played on a 9×9 grid divided into nine 3×3 boxes. The goal is simple to state: fill every row, every column and every box with the digits 1–9, each appearing exactly once. No arithmetic is involved — despite the numbers, Sudoku is pure deduction.
Every puzzle here is generated on your device and verified to have exactly one solution, so you can always reason your way to the end without guessing. Pick from three difficulties, tap a cell and enter numbers with the keypad or your keyboard. Conflicting digits are highlighted as you play, and a timer tracks your solve.
How to play
- Tap an empty cell to select it, then tap a number (or press 1–9 on your keyboard).
- Every row, column and 3×3 box must contain the digits 1–9 exactly once.
- Digits that conflict with another cell are shown in red.
- Use ⌫ to erase. Fill all 81 cells correctly to win.
Tips & strategy
- Start with 'scanning': pick a digit that appears often and find boxes where only one cell can hold it.
- Look for cells with only one possible candidate ('naked singles') — there's always at least one somewhere.
- Work box by box rather than jumping around; local constraints are the strongest.
- On hard puzzles, learn pairs: if two cells in a unit can only be {2,7}, no other cell in that unit can be 2 or 7.
Frequently asked questions
Do these puzzles always have a unique solution?
Yes. The generator removes clues only while the puzzle still has exactly one solution, verified by a solving algorithm — so pure logic is always enough.
Is guessing ever required?
No. Every puzzle can be completed by deduction alone. If you feel stuck, there is always a next logical step you haven't spotted yet.
What's the difference between the difficulties?
Harder levels start with fewer given digits (roughly 43 / 35 / 29 clues), which requires longer chains of reasoning.