How to play Sudoku
- Every row, column and 3×3 box must contain the numbers 1 to 9 without repeats.
- White numbers are given; the ones you enter appear in color.
- Turn on Notes to pencil in candidates. Correct numbers clear matching notes automatically.
- A wrong number turns red and counts as a mistake. Three mistakes end the game.
Tips to beat your high score
- Start with the number that appears most often and find where it fits in each box.
- Look for “naked singles”: cells where only one number fits.
- If a number can only go in one row inside a box, rule it out of that row in the other boxes.
Medals
Earn medals by reaching these scores on the default difficulty (harder ones have their own medals): 🥉 ≤ 10:00 min · 🥈 ≤ 6:00 · 🥇 ≤ 3:00. Every medal also gives you XP to rank up.
Why is Sudoku so addictive?
Sudoku is the most popular logic puzzle in the world: no math, just attention. Every solved cell unlocks the next, and completed rows and boxes flash in a satisfying chain reaction.
Frequently asked questions
Does every puzzle have a unique solution?
Yes. Each puzzle is checked by a solver before you see it, so there is exactly one valid solution.
Can I take notes?
Yes. Press the Notes button (or N on a keyboard) to write small candidate numbers in a cell.
Will I lose my game if I close the page?
No. Your puzzle, notes, mistakes and time are saved in your browser and restored when you come back.