Candidates and notes
Begin with cells that allow only one digit. Note mode records candidates without committing a value. Each confirmed digit removes that candidate from peers in its row, column, and box, often revealing the next single.
Sudoku
Fill each row, column, and three-by-three box with the digits 1 through 9 exactly once.
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How to play
Fill each row, column, and three-by-three box with the digits 1 through 9 exactly once.
- Select an empty cell and enter a digit from 1 to 9.
- Use notes to track candidates that may fit a cell.
- Complete every row, column, and box without repeating a digit.
Strategy tips
- Scan for cells with only one possible candidate.
- Check a number across both its rows and boxes.
- Use notes consistently and remove candidates after every confirmed entry.
Complete guide
Rules, scoring, and strategy
Sudoku places digits 1 through 9 so every row, column, and 3×3 box contains each digit once. It uses logic rather than arithmetic, with note mode available for tracking candidates.
Difficulty and progress
Easy puzzles expose more givens, medium requires more candidate interaction, and hard may require pairs or locked candidates. The progress metric counts filled cells; winning requires a valid completed grid.
Common mistakes
Do not guess while an unchecked house still contains a logical deduction. Keep candidate notes current because stale notes hide singles. When a contradiction appears, undo to the earliest uncertain entry instead of patching around it.
A repeatable solving order
Sweep rows for missing digits, then columns, then boxes. Search for digits that fit only one position in a house. Repeat after every placement. On harder boards, compare candidate pairs confined to the same two cells.
Questions players ask
Does Sudoku require guessing?
A well-formed unique puzzle should be solvable by logic, although difficult boards may require techniques beyond simple singles.
What does note mode do?
It stores small candidate digits in a cell without committing an answer or advancing completion.
Is the daily puzzle shared?
Yes. The UTC date and selected difficulty produce the same versioned puzzle seed for every player.