Killer Sudoku: Free Puzzles With Hints
Killer sudoku is sudoku with arithmetic: the usual rows, columns and boxes still hold digits 1 to 9 once each, but there are few or no given numbers. Instead the grid is split into dashed cages, and each cage shows a sum. The digits inside a cage must add up to that sum and cannot repeat. This killer sudoku generator builds a fresh random puzzle every time and checks that it has exactly one solution, so you never have to guess. Choose Easy, Medium or Hard, pencil in notes, and ask for a hint if you get stuck.
Killer Sudoku
Play killer sudoku online. Every puzzle has one solution, with cage sums, pencil notes, hints and a timer.
How to use the Killer Sudoku
- Pick a level and press New puzzle.
- Click a cell, then type 1 to 9 or use the number pad. Use arrow keys to move.
- Turn on Notes to pencil small candidate digits.
- Use Check to find wrong cells, Hint to reveal one cell, or Solve to see the answer.
Features
- Every puzzle has exactly one solution, verified by a solver
- Easy, Medium and Hard levels
- Dashed cages with sums, no repeated digit in a cage
- Pencil notes that clear themselves when you place a digit
- Mistake check, hint, reset and solve
- Timer and keyboard play, nothing to install
Frequently asked questions
How do you solve a killer sudoku?
Combine the normal sudoku rules with the cage sums. Start with small cages: a 2-cell cage with sum 3 can only be 1 and 2, and a 3-cell cage with sum 24 can only be 7, 8 and 9. Then use the rule that a row, column or box adds to 45 to find single cells.
Does every puzzle have only one solution?
Yes. The generator solves each puzzle with a backtracking solver and splits cages until exactly one grid satisfies all the rules. If the solver cannot decide quickly, it builds a new puzzle.
What are the cage combinations to remember?
Two cells: sum 3 is 1+2, sum 4 is 1+3, sum 16 is 7+9, sum 17 is 8+9. Three cells: sum 6 is 1+2+3, sum 7 is 1+2+4, sum 23 is 6+8+9, sum 24 is 7+8+9.
What is the difference between Easy and Hard?
Higher levels use larger cages, which give fewer single-cell clues, so you need more cage-sum reasoning. Easy puzzles have many small cages.
Is my progress saved or uploaded?
No. Everything runs in your browser and nothing is sent anywhere. Closing the page starts a fresh puzzle next time.