Expert Sudoku
Expert Sudoku puzzles need the long-range techniques: simple coloring, XY-Chains or a Jellyfish. They are the hardest Sudoku here, and still none of them needs a guess.
Expert puzzles need at least one of these techniques, and may use any easier one:
- Simple coloring
- Following pairs of a digit splits its cells into two colors; one color is true, which rules out the highlighted spots.
- Jellyfish
- A digit is limited to the same four columns in four rows (or the reverse), so it leaves the rest of those lines.
- XY-Chain
- A chain of two-candidate cells ends on the same digit at both ends; one end has it, so cells seeing both ends can't.
How to play
Sudoku is a number puzzle on a 9×9 grid divided into nine 3×3 boxes. Fill every empty cell with a digit from 1 to 9 so that each row, each column and each box contains every digit exactly once.
Every Sudoku here has exactly one solution, checked by a separate solver before it ships, and none of them needs a guess. The level is set by the hardest technique the puzzle truly needs, not by how many digits are given.
- Each row contains the digits 1 to 9 once.
- Each column contains the digits 1 to 9 once.
- Each 3×3 box contains the digits 1 to 9 once.
- The given digits cannot be changed.
Playing on this site
- Select a cell, then type a digit or tap it on the number pad. Arrow keys move the selection.
- Turn on Notes (or press N) to pencil in candidates instead of answers.
- Hint first points out any wrong digits, then names the next technique and shows where it applies before giving anything away.
- Your puzzle is saved in this browser, so you can come back to it later.