Sudoku

Sudoku

Fill the 9×9 grid so every row, column and 3×3 box contains the digits 1-9 exactly once. Choose a difficulty to begin — each level is graded by the hardest technique you'll need, not just by how many clues you start with.

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How To Play Sudoku

Every row, every column and every 3×3 box must contain each of the digits 1 to 9 exactly once. Tap an empty cell then tap a number (or use your keyboard) to fill it in. Cells that break a rule are highlighted in red until fixed.

Changing Your Mind

Nothing you enter is locked in. Tap the cell again to select it, then tap a different number to replace it or Erase to empty it — on a keyboard, Backspace, Delete or 0 do the same. Only the shaded starting clues are fixed.

Check

With Check on, any digit that doesn't match the puzzle's solution is shown in red with a line under it, so a mistake can't quietly spoil the rest of the grid. Turn it off if you would rather spot your own errors.

Notes & Candidates

Toggle Notes to switch the number pad into pencil-mark mode — tapping a number then marks or unmarks a small candidate digit in the selected cell instead of filling it in, so you can jot down possibilities as you deduce. Auto-fill candidates instantly seeds every empty cell with all of its currently legal digits as notes, which you can then erase as you rule them out. Placing a real digit automatically clears that digit from the notes of any cell it affects.

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