Free sudoku solver
Sudoku solver with step-by-step hints
Type in a puzzle from a book, a newspaper, or one of our sheets. Get one hint at a time, with the reasoning behind it, or reveal the whole solution. Works for 4×4, 6×6, and 9×9 grids, free and with no account.
Click a cell and type a digit. Arrow keys move between cells; Backspace clears one. Boxes are numbered left to right, top to bottom.
Enter the clues, then ask for a hint or the full solution.
How to use the solver
- Pick the grid size: 4×4, 6×6, or 9×9.
- Type each clue into its cell. Leave empty cells blank.
- Press Hint to see the next digit you can place and why, then fill it in yourself or let the solver do it.
- Press Solve to reveal the whole solution at once.
Prefer puzzles on paper? Browse printable sudoku with solutions
Techniques the hints explain
- Naked single
- A cell where every digit but one already appears in its row, column, or box. The remaining digit must go there.
- Hidden single
- A digit that has only one possible cell left in a row, column, or box, even if that cell could hold other digits.
- Locked candidates
- When a digit's only places in a box all lie in one row or column, it cannot appear elsewhere in that row or column. It also works the other way round, from a line into a box.
- Naked pair
- Two cells in a unit that can each hold only the same two digits. Those digits must go in those two cells, so no other cell in the unit can have them.
- Hidden pair
- Two digits that can only go in the same two cells of a unit. Those cells must hold those digits, so any other candidates in them can be removed.
- Naked triple
- Like a naked pair, with three cells sharing three digits between them.
- X-wing
- A digit with exactly two places in each of two rows, lined up in the same two columns. It must sit on one diagonal of that rectangle, so it is ruled out from the rest of both columns (or rows, the other way round).
Questions
- Is the sudoku solver free?
- Yes. The solver, its hints, and the full solution are free to use, with no account, no watermark, and no limit.
- How do the hints work?
- Each hint finds the simplest next move a person could make, starting with singles and moving to pairs, triples, and X-wings only when needed. If some candidates have to be ruled out first, the hint lists those steps before naming the digit to place.
- Why does it say my puzzle has more than one solution?
- A proper sudoku has exactly one solution. If more than one fits, a clue is usually missing or was typed into the wrong cell. Compare the grid with the original puzzle.
- What if the hints run out?
- A few very hard puzzles need techniques beyond the ones the hints explain. The solver can still find the solution: press Solve to see it.
- Which grid sizes can it solve?
- Standard 9×9 sudoku, 6×6 grids with boxes two rows tall and three columns wide, and 4×4 grids with 2×2 boxes.