Hard Jigsaw Sudoku Online
Free 9×9 jigsaw puzzles at hard difficulty — irregular regions, advanced technique territory.
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All-TimeHard Jigsaw Sudoku stretches the technique repertoire you've built up on Classic. With only 33–37 givens and irregularly shaped regions, you'll need hidden pairs, naked triples, X-Wing, and box-line equivalents adapted to the irregular regions. The Show Candidates button is especially valuable on Jigsaw because the eye can miss candidate placements inside a region that snakes across the grid. Sudoku247Online's solver verifies every Hard jigsaw puzzle has a single unique solution by pure logic before it ships, so when you crack one, the answer is correct by construction.