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Game Instructions & Description
How to Play Killer Sudoku
Play Killer Sudoku online for free in your browser. Killer Sudoku was made by the CrazyArcade team and follows the normal Sudoku rules: every row, column and 3x3 box must hold the digits 1 to 9 exactly once. On top of that, the grid is split into cages drawn with dashed outlines. Each cage shows a small sum in its top-left corner, and the digits inside the cage must add up to that sum without repeating. Every puzzle is generated in your browser when you start a game. The game builds a random solved grid, splits it into connected cages of mostly two to five cells, and then runs a solver that uses the cage sums to confirm the puzzle has exactly one solution. If it finds a second solution, it adds a starting digit or redraws the cages nearby until only one answer remains. Easy puzzles begin with about 22 digits already placed, Medium puzzles with about 8 to 13, and Hard puzzles start with an empty grid, so the cage sums are your only clues. When you select a cell, the strip under the board lists every set of digits that can fill its cage, and crosses out the sets that do not contain the digits already entered there. Notes mode lets you pencil in candidates, and a hint fills one cell with the correct digit. A wrong digit turns red and adds to your mistake count, and repeated digits in a row, column, box or cage are shaded. The timer stops when the grid is complete, and your best time and number of wins for each level are saved in your browser.
Controls & Interaction
Click or tap a cell to select it, then press 1-9 or tap the number pad to enter a digit. Use the arrow keys to move, Backspace, Delete or 0 to erase, N to toggle notes mode (or hold Shift while pressing a digit to add a single note), and H for a hint.
Pro Tips to Win
- Use the 45 rule: every row, column and 3x3 box adds up to 45, so subtracting the cages that sit fully inside a box tells you what the remaining cells must total.
- Start with cages that have only one possible combination, such as two cells adding to 3 (1 and 2) or two cells adding to 17 (8 and 9); the combinations strip shows these at a glance.
- Watch the crossed-out combinations in the strip after you enter a digit in a cage, because they narrow down which digits the other cells in that cage can use.
Frequently Asked Questions
Q: Does every Killer Sudoku puzzle have one solution?
A: Yes. Each puzzle is generated in your browser and checked with a solver that uses the cage sums. If more than one solution is possible, the game adds a starting digit or redraws nearby cages until only one solution remains.
Q: What is the difference between Easy, Medium and Hard?
A: Easy starts with about 22 digits already filled in and uses smaller cages. Medium starts with about 8 to 13 digits and adds larger cages of up to five cells. Hard starts with an empty grid, so you solve it from the cage sums alone.
Q: Are my best times saved?
A: Yes. Your best time and number of wins for each difficulty level are stored in your browser on this device.
