Sudoku
Fill the grid without repeating numbers. Pick one of four levels, use notes and hints that explain the why, play the daily sudoku, or print sheets to take with you.
A game is in progress. Start a new one?
This will erase your numbers and notes in this game. Restart it?
Arrow keys to move, 1 to 9 to type, Delete to erase, N for notes, H for a hint.
Type the sudoku numbers on the board or paste the sudoku below.
81 characters in a row, or 9 lines. Use 0 or a period for empty cells.
Settings
How to play
- Fill the grid so that every row, every column, and every 3 x 3 box contains the numbers 1 to 9 with no repeats.
- Select a cell and pick a number. Pick it again to erase it.
- With notes turned on, you write small candidates instead of the number. When you place a number, it is removed from the related cells.
- Keyboard: arrow keys to move, 1 to 9 to type, Shift + number for a note, Delete to erase, Ctrl + Z to undo.
- A hint explains why a number goes in a cell. If you make a mistake, “Check” marks the incorrect cells.
Your statistics
| Level | Won | Best without hints |
|---|
Printable sudokus
Makes sudoku sheets ready to print on A4, with the option to add the solutions.
How to use it
- Choose a level (Easy, Medium, Hard or Expert) and select New game. Every sudoku is generated on your device and has exactly one solution.
- Tap an empty cell and choose a number from 1 to 9 on the on-screen pad or with your keyboard. Choose the same number again to erase it.
- Turn on Notes to jot down small candidates. When you place a number, it is removed from the notes of the cells in its row, column and box.
- If you get stuck, ask for a Hint: it shows the cell and explains why that number goes there. “Check” marks the incorrect cells.
- When you finish the grid, your time is saved. Come back tomorrow for the daily sudoku, or print sheets from the printing section.
Frequently asked questions
Does every sudoku have only one solution?
Yes. Before showing you a sudoku, the generator checks that it has exactly one solution, so you can always solve it by deduction, without guessing.
How do the levels differ?
In the number of starting clues and in the techniques you need. Easy and Medium can be solved with naked singles and hidden singles. Hard calls for locked candidates and naked pairs. Expert demands more elaborate techniques, such as hidden pairs, naked triples or X-Wing, and some puzzles need even more.
What is the daily sudoku?
One sudoku per level that is the same for everyone that day. It changes every day at 03:00 UTC. If you solve it several days in a row, your streak is counted.
How do notes and hints work?
Notes are candidates you write in small print. With “Auto notes” they fill in by themselves. The hint looks for the simplest deduction and explains it, for example which numbers are already in the row, the column or the box. You can place it with a button or carry on by yourself.
Can I solve a sudoku from a newspaper or a book?
Yes. Switch to “Solve a sudoku”, type the numbers on the board or paste the text (81 characters or 9 lines). You can see the whole solution at once, or step by step with an explanation of each move.
How do I print sudokus?
Open “Printable sudokus”, choose the level, the quantity and how many fit on each sheet (1, 2 or 4), and select Print. It makes an A4 sheet and, if you want, another one with the solutions. You can also select Download PDF to save it as a file.
How to solve a sudoku
Every row, column and 3 x 3 box must contain the numbers 1 to 9 exactly once. Almost everything can be solved with two ideas.
- Naked single: only one number fits in a cell because the other eight are already in its row, its column or its box.
- Hidden single: a number can go in only one cell of a row, column or box, even if that cell allows other candidates.
When those two run out, the techniques of the higher levels come in: locked candidates in a box or in a line, naked pairs and triples, hidden pairs and X-Wing. The hint tells you which one you need and why, and you can also ask it to fill in the cell.
How to use notes
Pencil notes keep the small candidates of each cell. Turn them on with the N key or the “Notes” button and write several numbers in the same cell without fixing them. When you place a final number, the “Remove notes when placing a number” option clears the related candidates in its row, column and box. There is also an “Auto notes” button that fills in the possible candidates of all empty cells at once.
Check, mistakes and undo
The “Check” button marks the cells with incorrect numbers and tells you how many there are, without ending the game. If you turn on “Count mistakes”, every error adds to the counter and the error is not hidden. Undo and redo are unlimited, so you can try a technique and go back without fear.
Levels
- Easy: 36 to 40 starting numbers, only naked singles and hidden singles.
- Medium: 30 to 35 numbers, with the same techniques but less help.
- Hard: 26 to 29 numbers and some locked candidates or naked pairs.
- Expert: 22 to 25 numbers and advanced techniques.
Daily sudoku and printing
The daily sudoku is the same for everyone. If you want a sheet of paper, “Printable sudokus” makes an A4 PDF with several boards and a solutions sheet, and the “Solve a sudoku” mode accepts a pasted puzzle and solves it step by step.
Keyboard shortcuts
Arrow keys to move, 1 to 9 to type, Delete to erase, N to turn notes on and off, Shift + number for a quick note, H to ask for a hint, P to pause and Ctrl + Z to undo.
Updated on September 29, 2026