Eight free sudoku variants: jigsaw chaos sudoku, double chaos, calcudoku, thermo, kropki, killer, Sudoku X — and a mix of them all.
Every row, every column and every coloured region must contain the digits 1 to 9 exactly once. In Chaos sudoku the nine regions are irregular jigsaw shapes instead of the usual 3×3 boxes, so you read them from the colours.
In Double Chaos, the same puzzle appears in two grids with different region layouts that share a single solution — you need clues from both grids to solve it.
And in Calcudoku (KenKen-style) there are no given digits at all: fill a 4×4 or 6×6 grid where every outlined cage shows the sum, difference, product or quotient of its cells.
Four variants keep the classic 3×3 boxes and add one rule each. Thermo draws thermometers on the grid: along each one the digits increase from the bulb to the tip. Kropki marks neighbouring cells with dots: black for one digit double the other, white for consecutive digits, and no dot means neither. Killer replaces the given digits with dashed cages that show the sum of their cells. Sudoku X adds the two long diagonals, which also hold 1 to 9. Mix combines several of these in one puzzle.
Every puzzle is generated here and checked to have exactly one solution, so it can always be solved by logic alone. There are three difficulty levels per variant, pencil marks, a mistake check, and a print button for solving on paper. Six free printable PDF sheets are published every week, and each variant has a guide to its rules and a guide to solving it.
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New to chaos sudoku? Read the beginner's guide. · What is calcudoku? · All guides