Expert Sudoku — Extreme Difficulty
The hardest puzzles on the site — only for the most dedicated solvers.
Expert grids rarely fall to singles alone. Master the XY-Wing technique — the wiki's guide walks the three-cell pivot pattern step by step.
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All-TimeWhat makes a sudoku expert difficulty?
What makes a sudoku expert difficulty isn't how few numbers it starts with — it's the hardest technique the clue placement forces you to use. An expert sudoku begins with only about 19 to 21 given numbers, which sits at the top of the everyday ladder, just above Hard. With so much of the board blank, simple scanning and the intermediate moves that carry you through Hard run out of road. You reach a point where no cell has an obvious answer, and the only way forward is to spot an advanced pattern and use it to rule a candidate out. That's the line expert difficulty crosses: every puzzle still has one solution you can reach by pure logic, but finding the next step takes real technique, not a quick glance.
Expert vs Master vs Evil: how the top tiers compare
Expert, Master, and Evil are the three hardest tiers we generate, and they form a clean ladder. Expert is the top of the everyday range at 19 to 21 givens — tough, but solvable in a sitting. Step up to the Master tier and you drop to 18 or 19 givens, with longer chains of inference and fewer obvious footholds. Then step up to Evil sudoku, the floor at 17 or 18 givens — 17 being the proven minimum number of clues for any uniquely solvable 9×9 grid. The clue count tells only part of the story: what really separates the tiers is how deep you have to dig for each move. Expert asks for advanced single-step patterns; Master and Evil stack several of them into long deductive chains.
How to solve expert sudoku
To solve expert sudoku you'll need a deeper toolkit than the lower tiers ask for, because basic elimination stalls early. Start by filling in candidates — the small pencil marks listing every digit a cell can still take — then look for advanced patterns to thin them out. X-Wing eliminations remove a candidate across two rows or two columns at once; the swordfish pattern does the same idea across three rows or columns. When those stall, chain logic like the XY-Wing uses a pivot cell with two candidates to link two other cells and force a digit out. Naked and hidden pairs and triples round out the kit. Work patiently, lean on Notes and Show Candidates, and remember there's always a logical next move — the challenge is finding it, never guessing.
Expert sudoku questions
How hard is expert sudoku?
Expert sudoku is the hardest of the standard difficulty tiers — one rung above Hard. With only 19 to 21 starting numbers, basic scanning and intermediate moves won't get you to the finish; you'll need advanced techniques like X-Wing, Swordfish, and XY-Wing. Most solvers spend 40 minutes to over an hour on a tough grid. It's a real challenge, but every puzzle still has a single solution you can reach by pure logic.
How many starting numbers does an expert sudoku have?
An expert sudoku starts with about 19 to 21 given numbers, compared with 22 to 26 on Hard. But clue count isn't what sets the difficulty — what matters is the hardest technique the clue placement forces you to use. A grid with a few more givens can still be expert if the path to the solution runs through advanced patterns. Most of the board is left blank, so every placement has to be earned by logic.
What techniques do you need for expert sudoku?
Plan to use advanced patterns the easier tiers rarely require: X-Wing and Swordfish to eliminate candidates across rows and columns, XY-Wing chains when a pivot cell links three others, plus naked and hidden pairs and triples. Disciplined candidate tracking ties it all together — fill in the pencil marks first, then look for the pattern that thins them out. Our strategy guides walk through each technique step by step if you'd like to practise before diving in.
Is expert sudoku harder than hard sudoku — and easier than evil?
Yes on both counts. Expert sits one rung above Hard: Hard usually yields to intermediate moves, while Expert forces advanced patterns like X-Wing and Swordfish. It's also a step below Evil, which drops to 17 or 18 givens and stacks several advanced techniques into long chains of inference. The ladder runs Hard, then Expert at 19 to 21 givens, then Master at 18 or 19, then Evil at the floor of 17 or 18.
Are these expert sudoku puzzles free?
Yes — every expert sudoku on Sudoku247Online is free, freshly generated each time you play, and guaranteed solvable by pure logic with one unique solution. There's nothing to download and no sign-up to start. Create a free account if you'd like to play ad-free, earn XP, and save your solve times to the leaderboard.