How to play Sudoku
- Fill the grid so that every row, every column and every 3 × 3 box contains the digits 1 to 9 exactly once.
- Tap a square, then tap a number below (or type it). Tick Pencil marks to note candidates in a square. Mistakes are shown in red unless you turn that off.
- Stuck? Press Hint to reveal a square. When you finish, share your time: the link contains the same puzzle, so friends can race you on it.
Solving tips
Start with the easy wins. Look for a digit that can only go in one place in a row, column or box ("hidden single"), and for squares where only one digit is still possible ("naked single"). Scanning each digit from 1 to 9 across the grid finds many of these quickly. Pencil marks help on harder puzzles: once you have candidates written in, look for pairs, two squares in a unit that can only hold the same two digits, and remove those digits from the rest of the unit.
Every puzzle here is generated fresh in your browser and checked to have exactly one solution, so you never need to guess. Easy puzzles start with about 40 given numbers and expert ones with about 23, which require more advanced reasoning. Sudoku is a great daily workout for concentration and logical thinking, and highlighting the same digits and the current row, column and box makes it easier on a phone.
Does every puzzle have one solution?
Yes. Each puzzle is checked by a solver to make sure it has exactly one solution.
How do pencil marks work?
With Pencil marks ticked, tapping numbers adds or removes small candidate digits in the square instead of placing an answer.
Can I play the same puzzle as a friend?
Yes. Share your result after solving; the link opens the same puzzle.