Hard Sudoku
Tough grids with fewer clues and deeper solving paths.
Hard Sudoku is designed for focused sessions with patient elimination and careful mistake control.
Use notes mode and hints strategically when you want to push through advanced puzzles.
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Hard puzzles go beyond hidden singles and require techniques like naked pairs and pointing pairs. A naked pair is two cells in the same unit that both contain only the same two candidates — those digits can be removed from all other cells in that unit.
Pointing pairs occur when a digit in a 3×3 box can only appear in one row or column within that box. That lets you eliminate the digit from the rest of the same row or column outside the box.
Hard grids typically have fewer than 28 given clues. With so few starting digits, candidate lists are longer and the order in which you apply techniques matters. Work through naked singles and hidden singles completely before looking for pairs.
Mistakes are costly at hard difficulty because they can cascade through your candidate lists. Use notes mode from the start and double-check eliminations before committing to a digit.
The hint system supports hard puzzles fully — it can identify naked pairs and pointing pairs and walk you through the reasoning. If a puzzle feels completely blocked, a single hint is usually enough to unlock the next sequence of moves.
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