Train your brain
Improves logic, memory, and concentration.
Free Killer Sudoku Online
Difficulty
Error
0 / 3
Time
00:00
Score
1.850
Scoring
Killer Weekly Cup #38
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9×9 Sudoku board. Use the arrow keys to move between cells; Home and End go to the start or end of a row; Ctrl or Command + Home/End goes to the first/last cell on the board. Keys 1–9 enter a digit in the current mode; Shift + 1–9 adds a quick Note without turning Notes on; 0, Delete, or the numpad decimal key clears a cell; N toggles Notes, A toggles Auto Candidates, and Space pauses the game.
Selected cage
Select a cell
45
Select a cell to see the cage total and possible combinations.
Levels 1–2 only guide you and do not use a hint; level 3 applies the solving step and uses 1 hint.
Tap to enter · press and hold to add a NotePress 1–9 to enter · Shift + number for quick Pencil marks
Select an empty cell to see valid candidates.
Sound & controls
Auto candidates and Notes mode are remembered separately for Classic and Killer. Pause state and game progress are not synced as preferences.
Reduce stress
Helps you relax and reduce stress.
Completely free
Unlimited play, no registration required.
Track progress
Detailed statistics and achievement tracking.
Quick guide
View the full Killer Sudoku guide
What is Killer Sudoku?
Killer Sudoku combines the rules of a 9×9 Sudoku with sum cages. Each row, column, and 3×3 block must still contain 1–9 without repeats; the digits in each cage must add up to the small number in its corner, and digits may not repeat within a cage.
An effective approach is to prioritize cages with few combinations, use rows/columns/blocks to eliminate digits, then apply the Rule of 45 when a region is close to a known sum. Start on Easy if you are new to reading cages.
1Keep the standard Sudoku row, column, and 3×3 block rules.
2Add the cells in each cage to reach the target shown in its corner.
3No repeated digits within the same cage.
45Use the total of 45 in a row, column, or block to derive the missing digit.
Advanced Killer Sudoku
How to Play Killer Sudoku
Killer Sudoku strategies to learn
Start with how to read cages and sums, then learn the Rule of 45. Each guide focuses on one reasoning group so you can practice it separately instead of reading one overly long article.
Killer Sudoku strategy: how to read cages and eliminate combinations
Practical Killer Sudoku strategy: prioritize cages with few combinations, combine row/column/block rules, manage candidates, and use sums to open the board.
Rule of 45 in Killer Sudoku: How to Calculate Innies & Outies
Understand the Rule of 45 in Killer Sudoku: why every row/column/block totals 45, how to calculate excess or missing sums, and how to use innies/outies safely.
How to solve Sudoku: techniques from basic to advanced
A systematic Sudoku solving path: scan singles, manage candidates, use pairs, locked candidates, and advanced patterns without guessing.