A little focus. A little Sudoku.

Find a quiet moment. Fill your first square.

Press Play Sudoku to open your puzzle. A saved board resumes automatically in the same browser. Otherwise, a new 9×9 board is ready immediately.

Choose an empty square, then press a number below or beside the board. With a keyboard, use the arrow keys to move and 1–9 to enter a number. Dark starting numbers stay fixed; your entries appear in terracotta.

Nine numbers. Three simple rules.

Fill every empty square with a number from 1 to 9. Each row, each column and each outlined 3×3 box must contain all nine numbers exactly once.

There is no arithmetic to do. Look at the numbers already present to work out what can fit. Every new puzzle has one solution and can be solved using single candidates and numbers with only one possible position in a row, column or box.

Repeated numbers are highlighted in red. This checks for conflicts in the row, column and box; a number without a red highlight can still be incorrect. Complete the whole board without repeats to finish.

A few helpful tools, always close by.

Notes switches number entry to small pencil marks in empty squares. Press a candidate again to remove it. Placing a full number clears its own notes and removes that candidate from other squares in the same row, column and box.

Erase clears the selected entry or all its pencil marks. Undo restores the previous change, including notes removed from neighbouring squares. Hint enters the correct number in the selected editable square, replacing an incorrect entry if needed. Hints can be undone too.

Use Tab to focus the board, arrow keys to select a square, 1–9 to enter a number, N to toggle notes, Backspace or Delete to erase, and Ctrl/Command + Z to undo. Touch and mouse controls work directly on the board and number buttons.

Start where the board gives you the most clues.

Look for a row, column or box with only a few spaces left. For an empty square, rule out every number already present in all three groups. If only one number remains, you have your next move.

Then look at a missing number within one group. Even when several squares are empty, that number may fit in only one of them. Pencil notes help keep track as you work around the board.

Leave it here. Pick it up later.

The puzzle, entries, notes and up to 250 undo steps save after each change in this browser. Reloading restores your progress. Clearing site data removes the save; a different browser or device has its own puzzle.

New round creates a fresh puzzle. If you have made changes to an unfinished board, it asks before replacing your progress. On a narrow screen, New round and How to play are in the Game menu.

Sudoku is a local game for one player, with no multiplayer room, difficulty selector or time limit.