Killer Sudoku
Small sums. Satisfying deductions.
Every cage adds up.No repeated digits in a cage.
Preparing your puzzle…
Take your time.
Your puzzle is right where you left it.
Choose a cell, then a digit. Use 1–9 and the arrow keys on a keyboard, or the number pad below. Dotted cages add to their corner total, with no repeated digits. Pencil notes help you keep track of possibilities.
A familiar grid. A new way in.
Fill the grid with digits 1 to 9. Each row, column, and outlined three-by-three box must contain every digit exactly once. The dotted lines divide the grid into cages: the digits inside each cage must add up to the small number in its corner, and no digit can repeat within that cage.
A cage may cross a box boundary. Its no-repeat rule still applies even when two of its cells share no row, column, or box. A one-cell cage tells you its digit directly. Our puzzles are generated for this site and checked for exactly one solution.
Let the sums do some of the work.
Select a cell, then tap a digit. The selected cage is shaded, and its total, remaining sum, and empty cells appear beside the number pad. A two-cell cage totalling 3 must contain 1 and 2. A two-cell cage totalling 4 must contain 1 and 3: 2 and 2 would repeat a digit.
If a cage totals 16 and already contains 4 and 7, its last cell is 16 − 4 − 7 = 5. You must still check its row, column, and box. Combinations lists distinct remaining digit sets that fit the cage sum and entered digits; it does not choose their positions, and the Sudoku restrictions may rule out more possibilities.
The rule of 45 gives another useful starting point: every complete row, column, or box totals 45. Add cages that lie entirely inside one such unit. If they cover all but one of its cells, the missing digit is 45 minus their totals. A cage that crosses the unit boundary cannot be subtracted in full for this calculation.
Clear controls. Room to think.
Use Notes to record candidates instead of entering a number. Auto notes uses the current entries, cage sums, and Sudoku restrictions to fill possible digits. Entering a number removes its note from cells in the same row, column, box, and cage. If an entered number is wrong, it can also make later candidates misleading; Check can help you revisit those assumptions.
Undo and Redo revisit up to 200 actions, including pencil-note changes. A requested hint explains a useful step before you choose whether to apply it. Check highlights incorrect entries without ending the game. Complete every cell correctly to finish; filling the grid with mistakes does not count as a victory.
Earn eight achievements for useful progress, correct cages, and completed puzzles. Celebrations stay clear of the board. Your current grid, notes, and earned achievements save in this browser when storage is available. Pause stops the active-play timer, and a saved game waits for you to resume.
Can I repeat a number inside a cage?
No. Digits must be different throughout a cage, including cages that cross between boxes. Every cage must also reach its printed sum, while the ordinary row, column, and box rules remain in force.
Why does the cage panel turn red?
The current entries leave that cage without a valid completion. Its sum may be too high or too low, a digit may repeat, or the available positions may conflict with the Sudoku restrictions. You can erase or undo entries and keep playing. Red highlighting is a warning, not a game-over limit.
Are combinations the same as a hint?
Combinations is an arithmetic reference for the selected cage. It shows remaining digit sets based on the cage sum and entered digits, rather than selecting a cell or revealing its solution. A Hint requests an explained next step and counts as assistance immediately, even if you close it without applying it.
How do hints and Check affect achievements?
You can still complete a puzzle and earn its normal completion achievement. A hint-free achievement requires no requested hints during that whole attempt; an unassisted achievement requires neither hints nor Check. Using Undo, restarting the same puzzle, or reloading does not erase that history.
Will my game save if I leave?
Your current puzzle, notes, undo history, timer, and earned achievements save in this browser when storage is available. They do not transfer automatically to another browser or device. If saving is blocked, you can continue playing, but keep the tab open to retain the current puzzle.
What is the difference between Restart and New puzzle?
Restart clears your entries and notes while keeping the same puzzle and its recorded assistance history. It does not count an already completed attempt again. New puzzle replaces the current grid and starts another attempt. A confirmation protects a game that is in progress.
What are the keyboard controls?
Use the arrow keys to move, 1–9 to enter a digit, and Backspace or Delete to erase. N toggles notes; holding Shift while entering a digit adds a temporary pencil note. U and R undo and redo, P pauses, and Escape closes a hint or dialog or leaves full screen. On a phone, tap a cell and use the visible number pad and tools.
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