Sudoku
Fill the grid so every row, column, and box has 1-9.
↑ This is Sudoku running right here in your browser — no download needed.
About the game
Sudoku is a number-placement puzzle. Fill a 9x9 grid so each row, column, and 3x3 box contains the digits 1 through 9 exactly once.
How to play
Click a cell and enter a digit. Use the given clues to deduce the rest through logic. A valid puzzle has exactly one solution.
Tips & strategy
['Scan rows, columns, and boxes for the only possible spot.', 'Use pencil-mark candidates to track options.', "Tackle 'naked singles' - cells with one remaining choice - first."]
Advanced guide
Sudoku solving is a process of elimination. Begin with cells that have a single candidate, then use box-line reductions: if a digit can only appear in one row of a box, eliminate it elsewhere in that row. Patience and candidate tracking turn even hard puzzles into a satisfying routine.
History & origins
Modern Sudoku was popularized in Japan in the 1980s, though its roots trace to 18th-century Swiss mathematics.
Frequently Asked Questions
Do I need math to solve Sudoku?
No - it is pure logic; you only place digits 1-9 without arithmetic.
What if I make a mistake?
Most versions let you erase and retry; a contradiction signals an earlier error.
What is a candidate list?
A note of digits still possible for a given cell.
Are harder puzzles solvable by logic alone?
Quality puzzles are, though they may require advanced techniques.
How do I start a blank puzzle?
Look for cells where only one digit can fit given the clues.
What makes a puzzle 'evil' difficulty?
Fewer clues and the need for pattern-based logic beyond basic elimination.
Where can I play Sudoku for free?
Right on this page — Sudoku is embedded above, free, legal, and with no download or sign-up. Play with your keyboard on desktop or touch controls on mobile. Your best score is saved in your browser, so it's still there next time. Every game here is original or open-source, with links that stay valid.