Sudoku
Classic 9×9 Sudoku with a brand-new puzzle every game. Fill each row, column and 3×3 box with the digits 1 to 9. Every puzzle is generated to have exactly one solution, with pencil-mark notes, highlights for your row, column and matching digits, mistake checking, hints, unlimited undo and a best time for each of the four difficulties, from Easy to Expert.
How to play Sudoku
⌨️ Keyboard & mouse
- Click a cell, type 1–9
- Arrows move
- N
- notes
- Backspace
- erase
- H
- hint
- Ctrl+Z
- undo
- Free, no sign-up
- Plays in the browser
How Sudoku works
Fill the grid so that every row, every column and every 3×3 box contains each digit from 1 to 9 exactly once. The digits you start with are fixed; everything else is yours to work out. Every puzzle here is generated with exactly one solution, so it can always be reasoned out and never needs a guess.
Two techniques carry most of a game. A naked single is a cell where eight digits are already ruled out by its row, column and box, leaving one. A hidden single is the other way round: a digit that has only one square left in a row, column or box, even though that square could hold other digits too. Easy puzzles need only the first, Medium needs the second, and Hard and Expert need you to compare candidates across cells.
Pencil marks are there for exactly that. Turn notes on to jot the candidates for a cell, and when you place a digit the game clears it from every cell that can see it. Mistakes are flagged as you make them, hints fill in a single correct cell, and the clock only decides whether you beat your own best for that difficulty.
Tips for Sudoku
- Scan each 3×3 box for a digit that can only go in one cell.
- Use notes for cells with two or three candidates. Pairs often unlock the rest of a row.
- The highlights show your row, column and matching digits, which makes conflicts easy to spot.
