Sudoku is one of the best-known logic puzzles in the world. Fill the 9×9 grid with the digits 1–9 so that no digit repeats in any row, column or 3×3 box.

Every daily grid has exactly one solution and can be solved by pure logic, without guessing.

How to play

1. Select an empty cell, then a digit on the number bar.
2. Every row, column and 3×3 box must contain each digit from 1 to 9 exactly once.
3. Use notes mode to pencil in candidates.
4. The puzzle is complete when every cell is filled in correctly.

Tips

• Look for rows, columns or boxes that are missing only one or two digits.
• Check where a given digit can still go within a box: often only one cell is left.
• Notes make it easier to spot pairs that rule out other candidates.

Strategy

• Think in digits rather than cells. Take each digit from 1 to 9 in turn and sweep it across all nine boxes. This cross-hatching alone cracks the first half of most daily grids.
• When a digit inside a box is confined to a single row or column, it cannot appear in that row or column in the other boxes. This pointing elimination is often exactly what frees the one cell you were stuck on.
• Bring out notes when scanning stops producing new digits. Fill in candidates for a whole box or row and look for two cells that share the same two candidates: those two digits are locked there and can be removed from every other cell in that unit.
• Speed comes from accuracy. Every wrong digit is counted as a mistake and appears in your shared result, so when you are unsure, pencil it in instead of guessing.

A worked example

Here is an invented situation. The top-left box has four empty cells and is still missing a 7. Row 2 already has a 7 further right, and so does row 3, so inside the box the 7 must sit in row 1. Of the two empty cells in row 1, one has a 7 lower down in its column, which leaves exactly one cell. This is a hidden single: the cell itself could hold several digits, but the 7 has nowhere else to go.

Now check that cell's row and column. If placing the 7 leaves a row with only one gap, fill it with the missing digit straight away. The game also clears 7 from the notes in the same row, column and box, so your candidates stay current and the next safe move is often right in front of you.

History of the game

Modern Sudoku began as Number Place, a puzzle devised by the American Howard Garns and first published by Dell Magazines in 1979. The idea of filling rows and columns without repeats is older still: mathematicians call such grids Latin squares, and Leonhard Euler studied them in the 18th century.

The puzzle found its real home in Japan, where the publisher Nikoli introduced it in 1984 and gave it the name Sudoku, short for a longer Japanese phrase. The worldwide boom came in 2004 and 2005, when British newspapers began running it and the rest of the world quickly followed, turning it into the best-known number puzzle there is.

Frequently asked questions

Do I need maths?

No. The digits are just symbols; Sudoku is purely a logic puzzle.

Is every day the same difficulty?

The daily grids are medium difficulty, though where the given digits sit makes each day tricky in its own way. Every grid has a single solution and can be solved by logic alone.

Is there a hint if I get stuck?

Yes. Select an empty cell and the Hint button fills in the correct digit. Undo (or Ctrl+Z) takes back your last moves.

Can I play with a keyboard?

Yes. Arrow keys move between cells, 1-9 enter a digit, Backspace or Delete clears it, and P or N toggles notes mode.