Sudoku Solver
Pick a grid size, enter the numbers you already know, then solve the whole puzzle instantly or reveal just one more number. Runs entirely in your browser. Nothing you enter is ever uploaded.
What can you do?
GridSolve fills in a Sudoku grid from the numbers you already know. Solve the whole thing in one go, or ask for just one more number when you're stuck and want to keep solving it yourself. It works on the classic 9x9 grid as well as smaller 4x4 and larger 16x16 variants.
Curious why some puzzles need at least 17 starting numbers to work at all? Read Why Every Solvable Sudoku Needs At Least 17 Clues.
How it works
Every solve runs directly in your browser using a constraint-based backtracking search, the same general approach serious Sudoku engines use, so nothing is ever sent to a server. Your numbers are checked for row, column, and box conflicts before solving starts, so a mistyped puzzle gets a specific, friendly explanation instead of a wall of nothing.
Frequently asked questions
Is this free to use?
Yes. There's no sign-up and no limit on how many puzzles you solve.
Do you store the puzzle I enter?
No. Solving happens entirely client-side in your browser. See the privacy policy for details.
What grid sizes are supported?
4x4, 9x9, and 16x16. For 16x16, cells use 1 through 9 and then A through G for the values 10 through 16.
What happens if my puzzle has no solution?
The solver checks your numbers first. If two of the same number share a row, column, or box, it tells you exactly where. If the numbers look fine individually but the puzzle still can't be completed, it lets you know that too, so you can go back and double-check what you typed.