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Killer Sudoku and Sudoku Variant Guides

Free guides, tools and printable puzzles from CageDoku: learn Killer Sudoku from the rules to advanced techniques, explore seven more variants and look up any cage sum.

Learn Killer Sudoku

Killer Sudoku for beginnersThe rules, the six cage combinations worth memorising and your first puzzle.Killer Sudoku rulesCages, sums, no repeats and the 45 rule in two minutes.How to solve Killer SudokuEight proven techniques in the order you should try them.The 45 rule: innies and outiesTurn cage sums into free digits, with worked examples.Cage combinations chartEvery sum for 2- to 6-cell cages, unique combinations highlighted.Cage calculatorEnter a sum and size, add must-have or excluded digits, get every combination.Cage combinations cheat sheetA one-page printable reference for the combinations that matter.Solving tipsSeven techniques from unique combinations to fish.Advanced Killer Sudoku techniquesMulti-region 45, pairs of innies and outies, cage-line interaction.Is Killer Sudoku harder than Sudoku?The short, honest answer and what actually changes.Killer vs classic SudokuGivens versus cages: what is different and who should switch.Design your own Killer SudokuCage shapes, avoiding ambiguity and checking uniqueness.

Sudoku variants

Sudoku variants explainedEight variants in one sentence each.Best variants for beginnersWhich variant to try first, ranked by gentleness.Thermo SudokuThermometers, the range trick and four beginner tips.Arrow SudokuThe digits on the arrow add up to the circle.Kropki SudokuWhite and black dots between cells.Sandwich SudokuClues outside the grid sum the cells between 1 and 9.Anti-Knight (Chess) SudokuNo repeated digit a knight’s move apart.Sudoku X (Diagonal)Both diagonals contain 1–9 once.6×6 Sudoku2×3 boxes, digits 1–6 and a quick strategy.

Play and print

Printable Killer SudokuSix free puzzles with solutions. Print or save as PDF.Sudoku app with no adsWhat “No ads. Ever.” means in CageDoku and what is free or Pro.

Reference

Sudoku glossaryCage, innie, outie, hidden single and 20 more terms.About CageDokuWho makes CageDoku and how the puzzles are built.Press kitIcon, screenshots, facts and contact.

Cage-sum guides

2 cells, sum 3 · 2 cells, sum 4 · 2 cells, sum 16 · 2 cells, sum 17 · 3 cells, sum 6 · 3 cells, sum 7 · 3 cells, sum 8 · 3 cells, sum 9 · 3 cells, sum 10 · 3 cells, sum 20 · 3 cells, sum 21 · 3 cells, sum 22 · 3 cells, sum 23 · 3 cells, sum 24 · 4 cells, sum 10 · 4 cells, sum 11 · 4 cells, sum 29 · 4 cells, sum 30 · 5 cells, sum 15 · 5 cells, sum 35

Practice it in CageDoku

Free, ad-free Killer Sudoku and seven more variants. Hints name the technique and highlight the cells, so you learn why a digit goes where it goes.