AI Sudoku

Unique Solution  ·  Pencil Marks  ·  AI Hints
Difficulty
Difficulty
Medium
Mistakes
0
Time
0:00

How to Play

  • Fill the 9×9 grid so every row, every column, and every 3×3 box contains the digits 1–9 exactly once.
  • Tap a cell, then tap a number on the pad — or use your keyboard (1–9, Backspace to erase, arrow keys to move).
  • Pencil marks — switch to Candidate mode (the ✎ button) to jot small candidate digits, or tick Auto Candidate Mode to fill them in automatically.
  • Stuck? Press AI Hint for the next logical move — and an explanation of the technique.
  • Mistakes are highlighted in red, but you can always undo and keep going.

Every puzzle is logic-solvable — you never need to guess.

About the AI

Each puzzle is built by a randomised backtracking generator, then verified by a solver that confirms exactly one solution exists. Difficulty is set by how many clues remain and which techniques are required to finish.

The AI Hint engine reads your board live: it computes the candidate digits for every empty cell, applies logical eliminations (naked pairs, pointing pairs), then finds the next forced move — a naked single or hidden single — and names the technique so you learn the pattern.

Easy needs only single-candidate scanning. Hard demands the advanced techniques covered in the strategy guide.

Frequently Asked Questions

Does every puzzle have one solution?
Yes. The generator verifies a unique solution, so each puzzle is always solvable with pure logic — never guessing.

What do Easy, Medium and Hard mean?
They control how many clues are revealed (about 45 / 34 / 28) and which techniques you'll need — from simple scanning up to naked and pointing pairs.

How does the AI Hint work?
It computes every cell's candidates, eliminates logically, and finds the next forced single — then names the technique and fills it in.

What are pencil marks?
Small candidate numbers you note while reasoning. Add them in Candidate mode, or let Auto Candidate Mode keep them updated for you.

Is it free and mobile-friendly?
Completely free, no sign-up. The board and pad scale to any screen — play on phone, tablet or desktop.

More AI games?
Try AI Tic Tac Toe or browse the games hub on LK Forge.