Play free Classic and Killer Sudoku across five difficulty tiers — with daily challenges, real-time tournaments, 1v1 duels with Elo ratings, game replays, a puzzle solver, and a full Learning Hub. Built on the Internet Computer blockchain.
What Is Sudoku Challenge?
Sudoku Challenge is a free, full-featured competitive Sudoku platform. Fill a 9×9 grid so that every row, every column, and every 3×3 box contains the digits 1 through 9 exactly once. No math is required — every puzzle is solvable by pure logic. Beyond classic solo play, you can compete in real-time tournaments, climb a skill-based global rating ladder, and challenge other players to head-to-head duels.
Game Modes
Classic & Killer Sudoku — Unlimited puzzles at your chosen difficulty. Killer Sudoku adds cages: dashed groups with a target sum and no repeated digit.
Daily Challenge — Three fresh puzzles every day (Easy, Medium, Hard), with streak tracking and a daily leaderboard.
Tournaments — Create or join real-time competitive lobbies with live leaderboards and spectator mode.
1v1 Duels — Elo-rated head-to-head matches: same puzzle, same clock, the faster solver wins.
Training & Learning Hub — Practice specific techniques across five levels with a guided Next Step button.
Sudoku Solver — Enter any puzzle manually or by image, and get an instant step-by-step solution.
Five Difficulty Levels
Easy — Naked Singles only. Perfect for beginners.
Medium — Adds Hidden Singles and Locked Candidates.
Hard — Demands Pairs, Triples, Quads, and Unique Rectangles.
Extreme — X-Wings, Skyscrapers, Coloring, and more.
Diabolical — The toughest: XY-Chains, Finned Fish, and ALS.
With over 150,000 puzzles, you'll never run out of challenges.