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Sudoku AI Coach
Sudoku AI Coach is a free sudoku app that, when you're stuck, shows you where to look and how to think your way to the next number, instead of just giving it away. You can play it in your browser now; an Android version is on the way.
Play in your browser Learn the techniques
Why it exists
Most sudoku apps' hints just fill in a number: "this one is 7." They don't tell you why it's 7, or how to spot the same situation next time.
Sudoku is solved with a set of reasoning patterns (techniques). Once you understand them, you can solve harder puzzles on your own. I wanted an app that helps with exactly that.
Three-step hints
Hints come in three steps instead of revealing everything at once:
- Where to look — highlights the row, column, or box to focus on
- How to think — names the technique and explains what it tells you
- The answer and why — shows the number and why the others don't fit
You can stop after the first step and work it out yourself, or go all the way to check. If you've entered a wrong number, the app points that out before suggesting the next move.
Hints you can trust
The next move isn't found by AI. It's found by a solver that uses the same techniques people do, and every explanation is built from the reasoning it actually used. AI can sound convincing while being wrong, so it doesn't do the solving.
Puzzles are generated and checked by the same solver: every one can be solved without guessing, using only the techniques of its difficulty.
An owl AI coach
If a hint still doesn't click, ask the owl AI coach. It explains the same reasoning from the solver in different words.
What's inside
- Six difficulties: Beginner, Easy, Medium, Hard, Expert, and Master
- Daily puzzles (the same for everyone per date and difficulty) and unlimited free play
- A guide and practice puzzles for each technique
- Notes (candidates), fill in all candidates, undo and redo
- Records and rankings
- 71 languages
Price and ads
It's free to play. It may show ads to cover running costs.
Techniques you can learn (easiest first)
Each technique has its own guide with a worked example on the board.
- Hidden Single (only one place for it)
- Naked Single (only one number fits)
- Pointing Pair (lined up inside a box)
- Box/Line Reduction (a line decides the box)
- Naked Pair
- Hidden Pair
- Naked Triple
- Hidden Triple
- X-Wing
- Swordfish
- XY-Wing
- XYZ-Wing
- Skyscraper
- 2-String Kite
- Unique Rectangle
- BUG+1
- Empty Rectangle
- W-Wing
- Naked Quad
- Hidden Quad
- Finned X-Wing
- Jellyfish
Read on the site
FAQ
- Is it good for beginners?
- Yes. The Beginner level needs only the first two techniques. If you're new to sudoku, start with the rules page on the site.
- Can I play without installing anything?
- Yes. The browser version has the same puzzles, hints, and practice puzzles as the app.
- Do I ever need to guess?
- No. Every puzzle is checked to be solvable by logic alone.
- Which languages does it support?
- 71 languages, including English and Japanese. The guides are available in the same languages.