Killer sudoku combines the logic of classic sudoku with arithmetic cage constraints for a uniquely satisfying puzzle experience. In addition to the standard rule that every row, column, and 3×3 box must contain the numbers 1 through 9, killer sudoku groups cells into colored cages. Each cage has a target sum, and the numbers within a cage must add up to that sum without repeating. This added constraint introduces a whole new layer of deduction that makes killer sudoku feel fresh even for experienced classic sudoku players.
Unlike classic sudoku, killer sudoku puzzles typically start with no given numbers at all — every cell is empty. All information comes from the cage sums and the no-repeat rule. This means you must combine sudoku logic with arithmetic reasoning from the very first move. For example, a two-cell cage with a sum of 3 can only contain 1 and 2, immediately narrowing your candidates. Learning common cage sum combinations is the key to getting started with killer sudoku.
Our killer sudoku offers four difficulty levels from Easy to Expert. Start with easy killer sudoku if you are new to the format, or jump straight into hard killer if you want a serious challenge. Whether you prefer classic or killer mode, our strategy guide has tips to help you improve your solving speed and technique.