Free Online Sudoku
Fill the 9×9 grid so every row, column, and 3×3 box contains the digits 1–9. Choose easy, medium, or hard difficulty. Includes hints, notes mode, and undo. No download or registration needed.
How to Play Sudoku
- The 9×9 grid is divided into nine 3×3 boxes. Some cells are pre-filled as clues.
- Click an empty cell, then type or click a digit (1–9) to place it.
- Every row, every column, and every 3×3 box must contain each digit exactly once.
- Use Notes mode to pencil in candidate digits when you are not sure which number belongs.
- Use a Hint if you are stuck — it will reveal the correct digit for one cell.
- The puzzle is solved when all cells are filled correctly.
Difficulty Levels
- Easy — many clues given; solvable with straightforward naked-single logic. Great for beginners.
- Medium — fewer clues; requires hidden singles and some candidate elimination. Good for regular players.
- Hard — minimal clues; demands advanced techniques such as pairs, triples, and X-wings. A real challenge.
Sudoku Tips & Strategy
- Start by scanning rows and columns for digits that can only fit in one place (naked singles).
- Look for a digit that appears in only one cell of a box even if other candidates exist (hidden single).
- Use the Notes feature to track candidates and cross them off as you place digits.
- If two cells in a unit share only two candidate digits, no other cell in that unit can contain those digits (naked pair).
- Work in small steps: place one digit, then re-scan. Avoid guessing.
Frequently Asked Questions
- Is this Sudoku free to play?
- Yes — completely free, no sign-up or download required.
- Does a new puzzle generate each time?
- Yes, every game generates a fresh, unique puzzle using a backtracking algorithm.
- Can I play on mobile?
- Yes, the puzzle is fully touch-friendly and works on phones and tablets.