Select a cell, then tap a number to fill it in.
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Sudoku Luna is a beautifully crafted place to play sudoku online for free. Choose from four difficulty levels, sharpen your logic with smart hints that actually explain the technique behind every move, and compete in the global daily challenge.
A confident start
From your first certain move to the right level
Sudoku is solved by proof, not by speed. Read one row, column or box at a time, place only what is certain, then choose a level that matches the way you want to practise.
01
The three rules that keep every move honest
- 1Every row uses the digits 1 to 9 exactly once.
- 2Every column uses the digits 1 to 9 exactly once.
- 3Every 3×3 box uses the digits 1 to 9 exactly once.
02
See one certain move
The highlighted cell is the last gap in its row. The row already contains 1 through 8, so only 9 can belong there.
- 1Read the row
- 2Rule out every other digit
- 3Place 9 with certainty
03
Which level fits today?
The label describes the reasoning you can practise here, not a promise about speed or a number of clues.
Easy
- Best for
- Starting out or returning to the rules.
- You will practise
- Scanning for certain digits and using notes calmly.
- Move on when
- Straightforward scans no longer reveal a safe move.
Medium
- Best for
- You solve easy puzzles without guessing.
- You will practise
- Complete candidate notes and Naked Pairs.
- Move on when
- You keep candidates clean and can spot a clear pair.
Hard
- Best for
- You are comfortable working from candidate notes.
- You will practise
- Proven eliminations and patterns such as X-Wing.
- Move on when
- You solve hard grids with patterns instead of guesses.
Expert
- Best for
- You enjoy deliberate, advanced deductions.
- You will practise
- Verifying complex patterns such as Skyscraper.
- Move on when
- Stay here to practise precision rather than speed.
04
Continue with purpose
Choose one clear next step: learn the rules, practise a technique, inspect your own puzzle or take Sudoku to paper.
About Sudoku
Sudoku is a logic puzzle played on a 9×9 grid divided into nine 3×3 boxes. The goal is simple: fill every row, every column and every box with the digits 1 to 9 – without repeating a digit. Despite the numbers, no math is needed; sudoku is purely about logic and deduction.
How to play Sudoku
Start with the easy level and look for rows, columns or boxes that are almost complete. Use notes to keep track of possible candidates in each cell. When you are stuck, the smart hint shows you the next logical step and explains the technique – so you improve with every puzzle.
Why Sudoku Luna?
- Four difficulty levels from easy to expert
- Daily challenge with a global leaderboard
- Smart hints that teach real solving techniques
- Notes, undo/redo and automatic error checking
- Dark and light mode with an elegant design
- Print puzzles as PDF in multiple layouts
Frequently asked questions
Is Sudoku Luna really free?
Yes. All puzzles, the daily challenge, statistics and the print function are completely free to use.
Do I need an account to play?
No. You can play instantly. An account is only needed if you want to appear on the global leaderboard and sync statistics across devices.
How is the score calculated?
The score is based on difficulty, solving time, mistakes and hints used. Daily challenge streaks add a bonus of up to 50%.
Can I print puzzles?
Yes. The print page generates fresh puzzles as a PDF with 1, 2, 4 or 6 grids per page, optionally with solutions.