How to play sudoku
Put the numbers 1 to 9 into the grid so that no number repeats in any row, any column or any of the nine 3 by 3 boxes. That's the whole rule. There's no math involved; the numbers could just as well be nine colors.
By Emre Özen, updated October 7, 2026
The board
A sudoku grid has 81 squares: 9 rows across, 9 columns down, and 9 boxes of 3 by 3, marked with thicker lines. Some squares start with numbers in them. Those are the clues, and you can't change them. Your job is to fill every empty square.
When you're done, each row holds 1 through 9 once. So does each column. So does each box. A well-made puzzle has exactly one way to do that, which means you never have to guess. Every puzzle on this site is checked for that before you see it.
Your first moves
Start where the grid is crowded. Pick an empty square in a row, column or box that already has lots of numbers, and ask which of 1 to 9 are still allowed there. Cross off every number you can see in the same row. Then the same column. Then the same box. If one number is left, it goes in. Puzzle solvers call that a naked single.
The second move turns the question around. Pick a number, say 5, and one box that doesn't have a 5 yet. Look at which squares in that box could still take a 5. Often the 5s in nearby rows and columns block all but one square. That square gets the 5. This is a hidden single, and it's the move most people miss at first.
Those two moves are enough for every easy and medium puzzle here. Harder levels add pairs and patterns, explained on our sudoku strategies page.
Using notes
On paper, people pencil small numbers into the corner of a square to remember what's still possible. Online, that's what Notes is for. Tap Notes so it says on, pick a square, and tap the numbers you want to jot down. Tap a number again to remove it.
When you place a real number, the game removes that number from the notes in the same row, column and box. You can switch that off in Settings if you'd rather manage notes yourself.
Hints, mistakes and undo
- Hint fills in one square and says why it had to be that number. If you've picked a square, the hint goes there. If not, it picks the easiest open square. You get 6 hints per puzzle: enough to get unstuck, not enough to solve it for you.
- Mistakes are flagged the moment you make them: the square turns red, and a "Wrong move" banner appears above the board. You get three. The boxes above the board fill with a red X for each one, and the third mistake ends the game, so the puzzle starts again from the beginning. Notes never count as mistakes. Rather play without the limit, or find mistakes yourself? Both can be switched off in Settings.
- Undo takes back moves one at a time, including notes.
- Pause hides the board and stops the clock. The clock also stops on its own when you switch to another tab.
Keyboard shortcuts
| Key | What it does |
|---|---|
| Arrow keys | Move around the grid |
| 1 to 9 | Place a number (or a note, when Notes is on) |
| Backspace, Delete or 0 | Clear the square |
| N | Turn Notes on or off |
| H | Get a hint |
| Ctrl+Z (Cmd+Z on a Mac) | Undo |
Which level should I pick?
If you've never played, start on easy and finish two or three. Most people are ready for medium within a week. Hard is a real step up because single-option moves stop being enough; read the pairs section of the strategies page before you try it. Expert is for when hard puzzles start to feel routine.
Ready? Play an easy sudoku or try today's daily puzzles.
More sudoku
- Daily sudokuA new easy, medium and hard puzzle every day, the same for everyone.
- Easy sudokuPlenty of clues. Every move can be found by looking for single options.
- Medium sudokuFewer clues, same simple logic. A good daily level.
- Hard sudokuNeeds pairs and pointing pairs, not just singles.
- Expert sudokuNeeds X-wings or triples. Still no guessing.
- Printable sudokuLarge-print sheets for pencil and paper, with answers.
- Sudoku strategiesFrom hidden singles to X-wings, with examples.