Sudoku Solver

About this Sudoku Solver

This solver offers a number of features to help you improve your solving skills and practice solving strategies.

Solve Features

Enter the numbers of the puzzle you want to solve in the grid. You can solve the puzzle completely or work through it one step at a time using the buttons below the grid.

Button: Solve

Solves the puzzle completely. If the puzzle has more than one valid solution, you'll be notified that the one shown is not unique. Cells you entered remain bolded so you can tell your clues apart from the solved cells.

Helper Features

The solver provides analysis features that help you check progress and learn how to solve a puzzle step by step.

Button: Hint

Request a hint to find the next cell to solve. The solver first looks for a naked single — a cell with only one legal candidate — and falls back to constrained backtracking if no simple logical step is available. Conflicting digits must be resolved before a hint can be given.

Button: Clear

Resets the grid. Empties all cells so you can enter a new puzzle.

How the solver works

The solver first looks for naked singles — empty cells where only one digit is legal — drawing on the same techniques covered in our guides on Naked Pairs and advanced patterns like Swordfish. When no simple deduction is available it falls back to constrained backtracking. Conflicting digits are flagged in red, and you'll be warned if a puzzle has more than one solution.

Prefer to play instead of solve? Try our daily puzzles — the same hint engine is built in.