Killer Sudoku Expert – Play Free Online
Building a puzzle with a single solution…
Killer learning studio
Turn cage totals into proven moves
Killer Sudoku becomes clear when every cage is read together with the row, column and box around it. Start with the information that is forced, keep combinations visible, then let a complete unit prove the next step.
01
Three signals, one proof
- 1A cage total tells you which digit combinations can exist.
- 2No digit may repeat inside a cage, so the combination remains precise.
- 3Rows, columns and boxes still total 45, linking local cages to the whole grid.
02
A cage total becomes a safe digit
A two-cell cage totalling 3 has only the digits 1 and 2. When the row already contains 1, the open cage cell is proven to be 2 — no guess is involved.
- 1Read the cage total and its number of cells.
- 2Remove combinations that repeat a digit or conflict with the grid.
- 3Place only the remaining digit the evidence allows.
03
Four levels, one connected method
Each difficulty strengthens one Killer skill. Pick the level that matches your current evidence, then move on when the next technique feels explainable rather than merely familiar.
Easy
- Best for
- Your first cages and calm, verifiable openings.
- Practice focus
- Extreme two- and three-cell combinations.
- Ready to progress when
- You can use cage digits with row and box constraints.
Medium
- Best for
- Solvers comfortable with basic cage combinations.
- Practice focus
- The Rule of 45 across one row, column or box.
- Ready to progress when
- A missing total becomes a useful candidate restriction.
Hard
- Best for
- Players keeping clean candidate combinations.
- Practice focus
- Innies and outies across a useful boundary.
- Ready to progress when
- You can explain an inside or outside remainder.
Expert
- Best for
- Experienced solvers who combine several constraints.
- Practice focus
- Multi-unit totals of 90 and 135.
- Ready to progress when
- You can choose a region with a provable multi-unit remainder.
04
Continue with real Killer tools
Read the underlying method, practise its exact technique, verify a position in the solver or print a fresh Killer grid — each route keeps the same cage-first logic intact.
Killer Sudoku expert
Link several regions with one exact total
Expert Killer Sudoku is about disciplined multi-region reasoning. Individual cage sums remain true, but the decisive constraint often appears only when several rows, columns or boxes are treated as one total of 90 or 135.
First safe move
Choose two connected units with few boundary cages. Start from 90, subtract the crossing sums, then verify the remainder against candidates.
An expert-level routine
- 01
Finish every directly verifiable cage and single-unit 45 deduction before opening a larger region.
- 02
Choose a two- or three-unit shape whose total is known, then list only the cage sums that cross its boundary.
- 03
Check the derived remainder against candidates and no-repeat before making an elimination; an exact total never licenses a guess.
Expert
Expert technique: multi-unit 45
Two complete units total 90 and three total 135. A carefully chosen multi-unit region can expose a cage remainder that is invisible inside any one row, column or box.
Learn Rule of 45 across several unitsLearn Killer Sudoku step by step
Start with cage combinations, then build toward the Rule of 45, innies and outies, and precise cage exclusions.
Expert Killer Sudoku: common questions
What makes expert Killer Sudoku different from hard?
Expert grids require several constraints to work together. A useful sum may span multiple units, while ordinary cage combinations and a single 45-total are not enough to finish the deduction.
What is multi-unit 45 reasoning?
Each complete unit totals 45, so two connected units total 90 and three total 135. Subtract the sums of cages crossing that combined region to derive the exact remainder inside or outside it.
Explore Rule of 45 across several unitsHow do I choose a useful multi-unit region?
Prefer a region with few boundary-crossing cages and known cage totals. The fewer unknown boundary cells remain, the more likely the 90- or 135-total creates a precise combination.
Can expert Killer Sudoku be solved without guessing?
Yes. The purpose of advanced region sums is to create verifiable constraints. If an apparent move depends on choosing one of several unproven combinations, keep it as a candidate rather than guessing.
What should I practise before expert Killer Sudoku?
Be comfortable with cage combinations, the Rule of 45 and innies/outies first. Multi-unit reasoning works best when those smaller deductions are already routine.