About this sudoku
A free browser sudoku with no sign-up and no app. Every puzzle is generated fresh and checked to have exactly one solution — there is never a point where you have to guess between two valid answers. Pick Easy, Medium, Hard or Expert, or play the daily puzzle, which is the same grid for everyone in the world that day so the solve-time leaderboard is a fair comparison.
Difficulty here means what it should mean. Instead of counting how many squares are blank, each puzzle is graded by the hardest technique you actually need to finish it: Easy needs only singles, Medium adds pairs, Hard brings in pointing pairs, box-line reduction and wings, and Expert reaches a point where no single-step deduction exists and you have to test a candidate. Clue count is a poor guide on its own — a 17-clue grid is often easier than a 30-clue one, because the constraints are spread further apart.
How to play
Fill the grid so every row, every column and every 3×3 box contains the digits 1 to 9 exactly once. Click or arrow-key to a square and type a digit. Use Notes (Space, or Shift + a digit) to pencil in candidates while you narrow a square down; placing a digit automatically clears it from the notes of every square that can see it, and Undo puts those notes back. Check compares your grid against the answer, and Hint gives you the next logical step.
The hint is the part worth using deliberately. Rather than silently filling a square, it names the technique — "hidden single", "pointing pair", "XY-Wing" — and explains in one sentence why that square must hold that digit. Used a few times, it teaches you to spot the pattern yourself, which is the only thing that makes harder grids get easier. Hints and checks are both recorded alongside your time on the leaderboard, so an unaided solve is visible as one.
