About Sudoku
Play free Sudoku online with a new daily puzzle every day and unlimited games at four levels: easy, medium, hard and expert. There is nothing to download and no account to create, and your game saves automatically, so you can close the tab and pick up exactly where you left off.
Sudoku is the world's favorite logic puzzle. You get a 9×9 grid with a few digits already in place, and your job is to fill in the rest so that every row, column and 3×3 box holds the numbers 1 to 9 once each. No math is involved, just careful reasoning, and every puzzle on this page has exactly one solution that you can reach by logic alone, without guessing.
Pencil in notes, undo as often as you like, and when you get stuck, a hint shows you the next move and the technique behind it. Solve without help to post your time on the global leaderboard, and come back each day to keep your streak going.
How to play Sudoku
- 1
Choose a puzzle
Start with the Daily puzzle, the same grid for every player today, or pick Easy, Medium, Hard or Expert for an endless supply of practice puzzles. The clock starts when the board appears and pauses whenever you scroll away or switch tabs.
- 2
Find a cell with only one answer
Pick a digit and scan the rows, columns and boxes where it already appears. Wherever those lines rule out every cell of a box but one, that last cell must hold the digit.
- 3
Pencil in candidates
On harder grids, switch on Notes to jot the possible digits in a cell's corners. When you place a digit, it is removed from the notes of every cell it rules out, so your candidates stay tidy.
- 4
Check your work and ask for help
With Check mistakes on, an incorrect digit turns red right away. Tap Hint whenever you're stuck: it highlights the cell, fills it in and explains the logic in one line.
- 5
Complete the grid
Fill the last cell correctly to finish. You'll see your time, mistakes and personal best and, for the daily puzzle, how you compare with everyone who played today.
Controls
| Input | Action |
|---|---|
| Click or tap a cell | Select it (arrow keys move the selection) |
| 1–9 | Enter a digit (press it again to clear it) |
| N, or Shift + 1–9 | Toggle notes mode, or add a single note |
| Backspace, Delete or 0 | Erase the selected cell |
| U or Ctrl/Cmd + Z | Undo (unlimited) |
| H | Get a hint |
| P or Esc | Pause and hide the board |
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Sudoku tips and strategy
Start where the grid is busiest
Rows, columns and boxes that already have six or seven digits are the easiest places to find a sure move, and each new digit gives you more information elsewhere.
Cross-hatch one digit at a time
Choose a digit, say 7, and trace the rows and columns that already contain a 7 through each box. If only one open cell in a box survives, it's a 7. Working through all nine digits this way solves most easy puzzles.
Look for the last digit a cell can take
Sometimes a cell's row, column and box already contain eight different digits. The missing ninth digit must go there. This is called a naked single, and it is easy to miss when you only scan by digit.
Use pairs to clean up your notes
If two cells in the same row can only be 3 or 8, those two digits are claimed. No other cell in that row can be a 3 or an 8, so erase them from its notes. The same idea works for three cells and three digits.
Watch for pointing digits
If every possible spot for a 5 inside one box lies in the same row, the 5 for that box must sit in that row, which rules 5 out of the rest of the row outside the box. Hard puzzles lean on this move constantly.
Never guess
Every puzzle here can be solved by logic. If you feel like guessing, look again for pairs, pointing digits or an X-Wing, or tap Hint to see which technique unlocks the next step.
Sudoku rules
A Sudoku grid has 81 cells arranged in nine rows, nine columns and nine 3×3 boxes. Some cells start with a digit, called a given or clue. To solve the puzzle, place a digit from 1 to 9 in every empty cell so that:
- each row contains 1–9 exactly once,
- each column contains 1–9 exactly once, and
- each 3×3 box contains 1–9 exactly once.
The digits are only symbols, so you never add anything up.
Solving techniques, from singles to X-Wing
Singles are the bread and butter. A hidden single is the only place a digit can go within a row, column or box. A naked single is a cell where only one digit is still possible. Easy puzzles need nothing else.
Pairs, triples and pointing come next. A naked pair is two cells in one unit that share the same two candidates, so those digits can be removed from the rest of the unit. Pointing happens when a digit's candidates inside a box all line up in one row or column, clearing that digit from the rest of the line. Medium puzzles are built on these moves.
X-Wing sounds scary but is simple to picture. Suppose that in two different rows a 4 can only go in the same two columns. The two 4s must sit on opposite corners of that rectangle, so they fill both columns, and no other cell in those columns can be a 4. Hard puzzles also use Swordfish (the same idea across three rows), XY-Wings and short chains, while expert grids call for longer chains and unique rectangles. Our hints name the technique they use, which makes them a great way to learn.
Difficulty levels and the daily Sudoku
We grade each puzzle by the hardest technique it needs, not just by how many clues it shows:
- Easy (38–45 clues): singles only. Perfect for learning or a quick break.
- Medium (30–35 clues): needs pairs, triples or pointing digits.
- Hard (26–29 clues): needs an X-Wing, Swordfish, XY-Wing or a simple chain.
- Expert (22–25 clues): needs advanced chains, W-Wings or unique rectangles.
The daily Sudoku unlocks at midnight in your time zone, and everyone gets the same grid, so you can compare times with friends. Difficulty ramps up through the week: Monday and Tuesday are easy, Wednesday and Thursday medium, Friday and Saturday hard, and Sunday brings an expert challenge. Finish it to extend your daily streak and share a spoiler-free summary of your solve. For more daily brain teasers, visit our daily puzzles page.
A short history of Sudoku
The modern puzzle was invented by Howard Garns, a retired architect from Indiana, and first published by Dell Magazines in 1979 under the name Number Place. In 1984 the Japanese puzzle publisher Nikoli introduced it in Japan as Sūji wa dokushin ni kagiru ("the digits must be single"), soon shortened to Sudoku. Nikoli also popularized the elegant symmetric layout of the clues.
Sudoku went global after Wayne Gould, a retired judge from New Zealand, wrote a computer program to generate puzzles and persuaded The Times of London to print one in November 2004. Within months newspapers across Britain and then the United States were running daily grids, and the 2005 Sudoku craze made it one of the most played puzzles in the world. If you enjoy it, try its arithmetic cousin KenKen, the picture-logic of Nonogram, our logic puzzles, or browse all our puzzle games.
Frequently asked questions
Is this Sudoku free to play?
Yes. Every puzzle, including the daily Sudoku, is completely free and works in any modern browser on phone, tablet or computer. There's no download or sign-up, and your progress is saved on your device automatically.
Does every Sudoku have only one solution?
A properly made Sudoku does, and every puzzle here has been verified by computer to have exactly one solution. That means you can always reach the answer by logic, with no guessing required.
How many clues does a Sudoku need?
Mathematicians proved in 2012 that 17 clues is the minimum for a puzzle with a unique solution. Our puzzles range from 38–45 clues on easy down to 22–25 on expert, though the techniques required matter more than the clue count.
What time does the daily Sudoku change?
A new daily puzzle unlocks at midnight in your local time zone, and everyone playing on the same date gets the same grid. It is easiest early in the week and hardest on Sunday.
What makes a Sudoku hard?
Hard Sudoku puzzles can't be finished with singles alone. At some point you need a pattern such as a pair, a pointing digit, an X-Wing or a chain to rule out candidates before the next digit can be placed.
Do hints or mistakes affect my score?
Your ranking is based on time only. Mistakes are counted and shown but never end the game. Using hints or auto-notes marks the solve as assisted, so it still counts toward your stats and streak but isn't posted to the leaderboard.
Can I play Sudoku on my phone?
Yes. The board and number pad are built for touch, you can play full screen, and your game is saved if you switch apps or lock your phone.