Sudoku

How to play Sudoku

1. The grid has nine rows, nine columns and nine 3×3 boxes. Fill every empty cell with a digit from 1 to 9; the digits printed at the start are fixed.
2. Each row, each column and each box must end up holding every digit from 1 to 9 exactly once.
3. Pick a cell with a click or a tap, or move with the arrow keys, then type a digit or tap it on the number pad. Backspace or Erase clears the cell.
4. Turn on Notes, or press N, to pencil small candidate digits into a cell instead; Shift and a digit pencils one in directly.
5. Every puzzle has exactly one solution, and reasoning alone reaches it: no guess is ever needed.
6. The puzzle is solved when every cell is filled and no digit repeats in any row, column or box.

About Sudoku

Sudoku here comes in four levels, graded by the hardest technique a puzzle needs rather than by how many digits it starts with. Easy puzzles fall to singles alone: a cell with only one digit left, or a digit with only one place left in its row, column or box. Medium adds locked candidates and pairs, hard adds triples, the X-Wing and the XY-Wing, and expert needs a quad, the Swordfish, the XYZ-Wing or a chain of linked pairs.

Every day at midnight UTC brings a new daily puzzle at each level, the same for everyone. Solve it to put your time on that day's leaderboard, where the fastest times sit at the top. Practice deals a fresh puzzle whenever you want one, off the board.

Selecting a cell lights up its row, column and box and every cell holding the same digit, and a digit that clashes with another turns red (switch Conflicts off for a sterner game). Undo takes back any move, the clock stops while the game is paused or the tab is hidden, and your progress stays in this browser if you close the page.

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