Hey Product Hunt 👋 I built Sudoku247Online out of frustration. Every free sudoku site I tried fell into one of three buckets: ad-stuffed, stuck in 2010, or capped difficulty at "Expert" — which isn't actually hard once you've been playing for a while. The problem I wanted to solve: a clean, fast, no-signup sudoku app that respects both casual players AND people who want a real challenge. What ended up shipping: • Classic sudoku at 4 levels, plus two new harder tiers (Master at 18-19 givens, Evil at 17) • Killer Sudoku with cage sums • Unlimited printable puzzles (1, 4, or 6 per page) • A graduated hint system — Reveal Cell, Reveal Box, or free Show Candidates — instead of one big "give me the answer" button • A blog covering real solving techniques (Snyder notation, candidate mode, sudoku history) The build itself evolved more than I expected. I started thinking "just make a clean sudoku" and ended up rabbit-holing into pencil-mark UX, hint psychology, and how world champions actually take notes (turns out it's the opposite of what most apps teach). Would love feedback from puzzle fans here — especially anyone brave enough to try the Evil tier 😅 Try it: https://sudoku247online.com

Sudoku247Online

Free online sudoku with Killer mode and Evil difficulty

Free online sudoku with Killer mode and Evil difficulty