Sudoku

Every row, every column and every 3×3 box must contain the numbers 1 to 9, each exactly once. Some numbers are given at the start, and there is only one way to fill in the rest. You never need to guess: each number can be worked out from the others.

Easy and medium puzzles can be solved with singles only: a cell that can take just one number, or a number that fits in just one place. Easy gives 36 or more clues, medium about 28 to 32. Hard puzzles need pointing pairs, box/line reduction, or naked and hidden pairs and triples. Expert puzzles need an X-Wing, Y-Wing or Swordfish at least once.

A hint first checks for wrong numbers and shows them. Otherwise it finds the next step a person would take, names the technique, and highlights the cells involved. Press “Fill it in” if you want the number entered for you. Games where you used a hint don’t count towards your best time.

Small numbers you write in a cell to remember which numbers could still go there. Switch to notes with the pencil button or the N key. When you place a number, it is removed from the notes in the same row, column and box automatically.

Yes. Each day has four puzzles, one per level, and everyone gets the same ones, so you can compare times with friends. A new set starts at midnight on your device.

Your current game, best times and daily streak are kept in this browser only. Nothing is sent to our server, and there is no sign-up. Clearing your browser data removes them.