Sudoku
Fill the grid so every row, column and box has 1 to 9.
How to play Sudoku
Sudoku is a number puzzle for one player. The board is a 9×9 grid. It is split into nine smaller 3×3 boxes. When the game starts, some squares already show a number. These are the clues, and you cannot change them. Your job is to fill in every empty square.
Goal
Put a number from 1 to 9 in every square so that each row, each column and each 3×3 box holds every number from 1 to 9 exactly once. No number may repeat in a row, a column or a box. Every puzzle on this site has exactly one correct answer, so you never need to guess.
Step by step
- Pick a square. Tap or click it, or move around with the arrow keys. The row, column and box of that square light up, and the same numbers on the board are marked.
- Enter a number with the number pad under the board or with the keys 1 to 9 on your keyboard.
- Not sure yet? Turn on Notes (or press N) and add small pencil marks for the numbers that could fit. Placing a number removes that note from the squares around it.
- Made a mistake? Use Erase (or Backspace) to clear a square, or press Undo to go back one step.
- If the same number appears twice in a row, column or box, both squares turn red. Fix the clash before you move on.
Levels
Easy puzzles give many clues and can be solved by looking for squares where only one number fits. Medium puzzles give fewer clues. Hard puzzles give the fewest clues and need smarter steps, such as working with pairs of notes.
End of the game
The puzzle is solved when every square is filled and there are no clashes. A timer runs while you play and stops when you finish, so you can try to beat your best time. Your game is saved in this browser, so you can close the tab and come back later. When you finish, try a different number game such as Minesweeper.
Strategy tips
- Scan for one number at a time. Pick a number, say 5, and check each box. If a box has only one free square where 5 can go, write it in.
- Look for the last free square. When a row, column or box has eight numbers, the ninth square is easy. Rows and boxes that are almost full are the best place to start.
- Use notes on hard puzzles. Write every possible number in the hard squares. When a square has only one note left, that number is the answer.
- Find pairs. If two squares in a row hold the same two notes, such as 3 and 7, those numbers belong to those two squares. Remove 3 and 7 from the other notes in that row.
- Check boxes against lines. If a number can only go in one row inside a box, it cannot go anywhere else in that row in the other boxes.
- Never guess. Each puzzle has one answer that you can reach with logic. If you feel stuck, look at a different number or area of the grid.
Sudoku FAQ
Does every puzzle have only one answer?
Yes. Each puzzle is checked by a solver before you see it, so there is exactly one correct way to fill the grid.
What is the difference between Easy, Medium and Hard?
Easy gives about 38 clues and needs only simple steps. Medium gives about 30 clues. Hard gives fewer clues and always needs smarter steps, like pairs of notes.
How do pencil notes work?
Tap Notes or press N, then enter numbers to add or remove small marks in a square. Tap Notes again to go back to writing big numbers.
Will I lose my game if I close the page?
No. Your puzzle, notes and time are saved in this browser. Open the page again to carry on where you left off.
