Sudoku Solver

How it works

The solver tries a digit in the first empty square, checks it against the row, column and 3×3 block, and moves on. If it hits a dead end it steps back and tries the next digit. This is called recursive backtracking. It runs entirely in your browser, and nothing you type is sent anywhere.

If the puzzle can't be solved, or has fewer than 16 starting numbers (too few to have one answer), the button will say so. View the code on GitHub.