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 — Easy, Medium and Hard puzzles every day in Classic and Killer, the Classic Daily Challenge with its leaderboard, and the Daily Triple — three elite puzzles on one combined leaderboard. Streaks and badges keep the run going.
Tournaments — Open or join real-time lobbies (Easy, Medium or Hard, 15 to 60 minutes) 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 by hand, as text or from a photo, and get the solution — then play it with the step-by-step Next Step coach.
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 146,764 graded Classic puzzles and a 50,000-puzzle Killer pool, you'll never run out of challenges.