How to Play Killer Sudoku
Select an empty cell, then enter a digit using the number pad or keyboard. The small number in the top-left cell of each dotted cage is its target total. Combine that total with the surrounding Sudoku numbers to narrow your choices. Fixed starting numbers cannot be changed.
Use Notes for candidates, Erase to clear an entry, and Undo to revisit a move. Hint fills one correct number. Fast input lets you select a digit before tapping cells. Pause covers the board and stops the active-play timer.
Killer Sudoku Rules
- Each row, column and 3×3 box must contain every digit from 1 to 9 exactly once.
- Digits inside each cage must add up to its target sum.
- A digit cannot repeat within a cage, even across different boxes.
- Finish all 81 cells with valid Sudoku units and correct cage totals to complete the puzzle.
Explicit conflicts are highlighted and count as mistakes. A partial cage is not marked wrong just because an entry differs from the solution. There is no forced mistake limit.
Difficulty Levels
Choose from 40 puzzles: ten each in Easy, Medium, Hard and Expert. Easy uses smaller cages and more starting numbers; higher levels generally use larger cages and fewer starting numbers. These initial difficulty groups describe the puzzle structure rather than a formal human-solving rating. Every puzzle has one verified solution.
New Game cycles through a shuffled set without repeating a puzzle until the set is exhausted. Progress, notes, score and Best Times are saved locally and separately from standard Sudoku. Hint-assisted games do not qualify for Best Time.
Killer Sudoku Tips
- Start with single-cell cages and small totals: a two-cell cage totaling 3 must contain 1 and 2.
- Each complete row, column or box totals 45. Compare it with cages contained in that area.
- A cage gives a set of possible digits, but rows and columns determine where they belong.
- Use Notes to track alternatives, then cross-check the cage and all three Sudoku units.
Frequently asked questions
What is Killer Sudoku?
Killer Sudoku combines standard Sudoku with sum cages. Fill each row, column and 3×3 box with 1–9, while making every cage add up to its small target number.
Can a number repeat inside a cage?
No. Digits in a cage must be distinct, even when its cells lie in different rows, columns or boxes.
Do these puzzles have a unique solution?
Yes. All 40 static puzzles have been checked for exactly one solution under the Sudoku and cage rules. Some puzzles include fixed starting numbers.
How do Notes and Hint work?
Notes record candidates in an empty cell. Hint supplies one correct number in the selected editable cell, or the next unfinished cell. Undo restores the previous move, including notes and mistakes.
When does an entry count as a mistake?
An entry counts as a mistake when it repeats a digit in a row, column, box or cage, pushes a cage over its target, or fills a cage with the wrong total. Mistakes do not end the game.
Can I play on mobile and save my progress?
Yes. Touch controls, four difficulty levels and local progress saves are available without an account. Sound is optional, and reduced-motion preferences are supported. Hints make a game ineligible for Best Time.
