About Sudoku Chaos

Sudoku Chaos is a free puzzle site run as a personal project by Willem Mevius. It grew out of a love for jigsaw sudoku and has become a small family of variants: Chaos and Double Chaos, Calcudoku, Thermo, Kropki, and Mix — plus a daily puzzle with leaderboards for players with a free account.

Where the puzzles come from

Every puzzle is generated by our own engine, on our own servers — nothing is copied from books or other sites. Before a puzzle is served, a solver proves that it has exactly one solution and never requires guessing; a puzzle that fails that proof is thrown away. The daily puzzle is the same for every player worldwide.

The book

Prefer paper? Sudoku Chaos, Volume 1 collects 72 chaos and double chaos puzzles in a 6×9 book with full solutions, available on Amazon as paperback and hardcover, in five languages.

Contact

Questions, bug reports, puzzle ideas, or anything about your data: write to privacy@sudokuchaos.com. The privacy policy explains what the site stores (very little) and why.