Sudoku
Fill the 9×9 grid so every row, column and box contains digits 1–9.
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Sudoku
How to use
- 1
Choose a difficulty and tap any empty cell to select it.
- 2
Type a number or use the number pad — enable Notes mode to pencil in possibilities.
- 3
Use hints if you're stuck — fill every cell correctly to win!
Free Sudoku Puzzle Online — Play Easy, Medium & Hard Sudoku
Play free Sudoku puzzles online with three difficulty levels. Fill the 9×9 grid so every row, column, and 3×3 box contains the digits 1–9. No signup required.
Skycally's Sudoku generates a fresh puzzle every game across three difficulty levels: Easy (many cells pre-filled), Medium (balanced challenge), and Hard (minimal clues for experienced solvers). Click or tap any empty cell, then type or tap a number to fill it. Conflicting entries are highlighted automatically so you can catch mistakes immediately.
Sudoku is a logic puzzle played on a 9×9 grid divided into nine 3×3 boxes. The rule is simple: fill every empty cell with a digit from 1 to 9 such that each row, each column, and each 3×3 box contains every digit exactly once. No arithmetic is required — just logic and deduction.
The puzzle has a rich history: it was popularized by Japanese publisher Nikoli in 1986 under the name Sūdoku (数独, meaning 'single number'). Before that, similar puzzles existed in French newspapers in the 1890s. Today Sudoku appears in newspapers, magazines, and apps worldwide, and is one of the most popular logic puzzles ever created.
For beginners, start with Easy mode and look for rows, columns, or boxes that only have one empty cell — those can be filled immediately. As you improve, learn techniques like naked singles, hidden singles, and box-line reduction. Hard puzzles may require more advanced techniques like X-wing or swordfish patterns.
Frequently Asked Questions
How do I play Sudoku?
Fill every empty cell in the 9×9 grid with a digit 1–9 so that each row, each column, and each 3×3 box contains every digit exactly once. No cell can repeat a number in its row, column, or box.
What are the three difficulty levels?
Easy has many pre-filled cells and can be solved with basic techniques. Medium requires some deduction. Hard has minimal clues and requires advanced logic techniques.
Does the puzzle highlight mistakes?
Yes. Cells that conflict with another number in the same row, column, or box are highlighted in red automatically.
Is every puzzle solvable?
Yes. Every generated puzzle has exactly one valid solution, which is confirmed before the puzzle is presented.
Can I use pencil marks / notes?
Check if the tool supports a note mode — some implementations include a toggle for candidate numbers.
What is a naked single?
A naked single is a cell where only one digit is possible — all other digits already appear in the same row, column, or box. Finding naked singles is the most basic solving technique.
Is my progress saved?
Progress is kept while you have the browser tab open. Refreshing the page starts a new puzzle.
Does this work on mobile?
Yes. Tap a cell to select it, then tap a number from the on-screen number pad. Fully responsive for smartphone and tablet play.
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