How to Play Sudoku
- Tap the board or Start New Game to enter. The opening tap does not place a digit.
- Select an empty cell, then tap a number from 1 to 9. Tap the × key to clear your entry.
- Every row, column, and 3×3 box must contain each digit from 1 to 9 exactly once.
- Framed digits are starting clues and cannot be changed. Corner dots mark one group of repeated digits; you can revise your entries.
- Hint previews an explanation. Apply places the digit and spends one hint; Cancel leaves the board unchanged.
- Fill the grid without repeats to finish. Exit returns to this page; Back to Game resumes until you reload the page.
One grid, three rules
Sudoku is a number placement puzzle, also called Number Place. The digits are labels: there is no adding or multiplying. Each digit must appear once in its row, once in its column, and once in its 3×3 box.
Sudoku Strategy
1. Find the last missing digit
This row has 1, 2, 3, 4, 6, 7, 8, and 9. The only missing digit is 5, so the marked cell must be 5. The same check works for a column or a 3×3 box.
Before placing a digit, check the other two groups too. If 5 is already in this cell's column or box, revisit an earlier entry: the groups disagree.
2. Eliminate candidates
Suppose a cell's row is missing only 2 and 5. Its column already contains 2, so 2 is ruled out. If its box has no 5, the only candidate left is 5. This is a naked single.
Several candidates left? Inspect another cell rather than entering one as a certainty. You can track candidates on paper; this version's number pad enters full digits, with no pencil-note mode.
Look for a hidden single
Sometimes a cell allows several digits, but one digit has only one possible place in its row, column, or box. That digit belongs there. Our hints can explain naked singles and hidden singles; they do not cover every advanced technique.
Difficulty and prepared puzzles
Each board comes from a prepared collection checked for one solution. Easy, Medium, Hard, and Expert aim for fewer starting clues as the level rises. A puzzle may retain extra clues to preserve uniqueness. These labels are not technique ratings, and the supported hint methods may not finish every puzzle.
Free Sudoku, no ads or download
The game is free to play in your mobile browser, with no ads, account, or app to install. Time, Moves, Best, and Skill stay beside the board. Your best time is saved in this browser for each difficulty; an unfinished board is not restored after a reload.
FAQ
What is Sudoku?
Sudoku is a number placement puzzle. The goal is to fill a 9×9 grid so that every row, every column, and every 3×3 box contains the digits 1 through 9 exactly once.
How do I play Sudoku?
Tap the board to enter the game without placing a digit. Then select an empty cell and tap a number from 1 to 9. Use the × key to clear an entry; framed starting clues cannot be changed.
Does this version save my best time?
Yes. Your best solve time for each difficulty is saved in this browser.
Is Sudoku a logic game?
Yes. Sudoku uses constraints from rows, columns and 3×3 boxes. Prepared puzzles are checked for one solution; the difficulty labels do not rate the deduction techniques needed to solve them.
What does the Hint button do?
Hint previews a logical single and explains the digit or its only possible place. Apply fills the cell and uses one hint; Cancel keeps your board and hints unchanged. If no supported deduction is available, no hint is spent.
A Brief History of Sudoku
Nikoli introduced the American puzzle Number Place to Japanese readers in 1984 and shortened its Japanese title to Sudoku. In 1986 the publisher adopted symmetrical starting-clue patterns. Read Nikoli's account of the rules and history.