Sudoku

Fill the 9×9 grid so that every row, every column and every 3×3 box contains the digits 1 through 9 exactly once.

The puzzle starts with some cells already filled in — these given clues cannot be changed.

Select an empty cell and enter a digit. Conflicting digits are highlighted so you can spot mistakes early.

Use notes (pencil marks) to keep track of candidate digits for a cell.

The puzzle is solved when the whole grid is filled correctly.

• Click or tap a cell to select it, then type 1–9 or use the on-screen number pad.
• Press Backspace, Delete or 0 to erase a cell.
• Use the arrow keys to move between cells.
• Toggle the pencil icon to enter notes instead of final answers, and use the hint button when you're stuck.

• Scan for rows, columns or boxes that are nearly complete — the last missing digits are free wins.
• Look for 'naked singles': cells where only one candidate digit remains.
• Use notes systematically on hard puzzles; guessing without notes usually backfires.
• If two cells in a box share the same two candidates, those digits can be eliminated from the rest of the box.