🔢 Sudoku Solver

Solve any puzzle instantly

Steps:
Time:
✓ Solved
✗ No solution
Copied!
← Back to Thinker Toolbox

How to Use This Sudoku Solver

  1. Enter your puzzle Type the numbers from your Sudoku puzzle into the grid. Use the number keys 1–9 for given digits; leave empty cells blank.
  2. Choose the grid size Supports 4×4, 9×9, and 16×16 puzzles.
  3. Hit Solve The solver finds the solution using constraint propagation and backtracking. Most 9×9 puzzles solve instantly.
  4. View the solution The solved numbers appear in a different colour so you can see which cells were filled in.

Use Cases

Stuck on a puzzle? We've all been there. you've spent 20 minutes on a Sudoku and hit a wall. Enter what you've got and the solver will complete it. You can also use it to check a single cell you're unsure about rather than revealing the whole solution.

Learning strategies. By comparing the solver's solution to your partial solution, you can see where you went wrong and learn new solving techniques. The solver uses pure logic (constraint propagation) before falling back to trial-and-error, so you can see which cells are logically determined vs guessed.

Solving 16×16 puzzles. Hexadecimal Sudokus (using 0–9 and A–F) are much harder to solve by hand. This solver handles them effortlessly, which is useful when you've spent hours on a puzzle that has you beaten.

Frequently Asked Questions

Can every Sudoku be solved?

Only valid Sudokus have a unique solution. If you enter an invalid puzzle (contradictory clues), the solver will tell you it can't be solved. If a puzzle has multiple solutions, the solver will find one of them and indicate that it's not unique.

What's the difference between 4×4, 9×9, and 16×16?

4×4 uses numbers 1–4 in 2×2 boxes. good for beginners and children. 9×9 is the standard puzzle with numbers 1–9 in 3×3 boxes. 16×16 uses 0–9 and A–F in 4×4 boxes. much harder and more time-consuming to solve by hand.

Does the solver work offline?

Yes. Once you've visited the page, it works offline. The solving algorithm runs entirely in your browser with no server needed. Handy for solving puzzles on a train or plane.

Is my data private?

Yes. the solver runs entirely in your browser. Your puzzle data never leaves your device.

Why Use This Sudoku Solver?

It handles 4×4, 9×9, and 16×16 puzzles, solves instantly, and works offline. No pop-ups, no "download our app" banners, no tracking. Just a clean solver that does its job. The 16×16 support sets it apart from most online solvers that only handle standard 9×9.

Works offline · Built with ♥ · About · Privacy · Terms · Contact

🍪 This site may use cookies for analytics. You can accept or reject personalised advertising.