Solve any Sudoku instantly

How to use the solver

1. Tap a cell to select it, then tap a shape in the palette to place it. Prefer the keyboard? Select a cell and press 1 to 9 to place the matching shape, use the arrow keys to move, and Backspace to clear.
2. Place every starting clue exactly as it appears in your puzzle. You can press Load sample to see it work first.
3. Press Solve for the full answer. The shapes it worked out appear faded so you can tell them from your clues.
4. Or press Step by step to learn as you go. It reveals one cell at a time and names the technique it used, like a naked single or a hidden single. Use Next step, Auto-play, or go back to editing.
5. Press Clear to start over, or change any cell to adjust the puzzle and solve again.

Shapes, not numbers

This solver speaks Shapedoku. Instead of the numbers 1 to 9 you place the same nine glowing symbols the game uses - triangle, hexagon, circle, crystal, heart, diamond, square, crescent moon and lotus. The logic is exactly classic Sudoku underneath: every row, column and 3x3 box ends up with each symbol exactly once. If your puzzle is written with numbers, just map 1 to 9 onto the shapes in that same order.

How the solver works

Under the hood it uses backtracking, the classic approach to Sudoku. It finds the first empty cell, tries the smallest legal number, and moves on. If it ever reaches a dead end, it steps back and tries the next option. Because a well made puzzle has exactly one solution, this search always lands on the correct board. If your clues break a rule or have no possible answer, the solver tells you instead of guessing.

Want to solve it yourself?

A solver is great for checking an answer or unsticking a tough spot, but the real fun is doing it by hand. If you want to sharpen your skills, read our Sudoku tips and strategies, learn naked and hidden singles, then put them to work in a fresh game.