Sudoku solver

Enter and check your puzzle

Use digits 1–9 in the grid and leave unknown cells blank. Arrow keys move between cells. Repeated digits in a row, column or box are highlighted. You can also paste an 81-cell puzzle using zeros or dots for blanks, with optional spaces and line breaks.

Check and solve searches for up to two solutions. A unique result means the search completed and proved there is exactly one solution. Multiple means at least two were found; any displayed grid is only one possible answer. No solution means the entered clues cannot all be true, even if no clues are directly repeated.

Request one logical step

Show next step looks for a naked single, where a cell has one candidate, or a hidden single, where a digit has only one place in a row, column or box. The explanation names the cell and reason. Apply the step only when you want to place it; Undo step restores the previous grid.

Hints do not reveal the full answer. If no single is available, the tool says so: it does not label a search guess as a logical deduction. The full solver uses backtracking; this version does not explain advanced solving techniques.

Understand the search limit

The search is bounded at 50,000 visited states to limit browser work. A limit result is inconclusive, not a claim of uniqueness or impossibility. Add more correct clues and try again. Enter all given clues rather than assuming a sparse board represents a unique puzzle.

The grid is processed locally without an account. It is not saved across reloads and is not sent to our servers or included in tool-use analytics. The example is PaperFox’s original teaching board from our Sudoku techniques guide.

Play or learn Sudoku

• Play Sudoku
• Read the rules
• Study worked technique examples

Questions

• Can a puzzle have no repeated clues and still have no solution? Yes. Clues can contradict each other indirectly. A completed search can prove no solution even when there are no immediate duplicate digits.
• Do you prove uniqueness? Only when the search completes with exactly one solution. Finding two proves multiple solutions; reaching the search limit is inconclusive.
• Will asking for a hint show the entire answer? No. The next-step action shows only an available naked or hidden single, with its reason. Use Check and solve if you want a solution grid.