Free Printable Evil Sudoku

Free printable evil sudoku puzzles — the hardest tier we generate, sitting at the proven theoretical minimum of 17 to 18 given numbers per grid. Below 17 givens, mathematicians have shown that no sudoku puzzle can have a unique solution. Evil grids live at that floor: every starting number matters, every empty cell is a candidate web until you crack it open, and every solve is genuinely earned. Expect ninety minutes to several hours of focused work on a fresh evil puzzle, especially if it features the longer techniques the difficulty regularly requires.

The technique landscape at evil is broader than the ones below it. You will work with every pattern from expert and master — X-wings, swordfish, hidden triples, naked quads, XY-wings — but you will also need the more exotic chains: XYZ-wings, W-wings, simple colouring, multi-colouring, and the first proper forcing chains. Most evil grids resolve through a combination of three or four advanced techniques stacked together, with each move shrinking the candidate set by exactly one digit per cell. Nothing about an evil puzzle is guesswork — the path to the unique solution is always reachable by logic — but the path is rarely short.

This is the tier where paper solving is no longer a preference but a competitive advantage. You need the full candidate notation visible across the entire grid at once to spot the patterns that evil grids hide. A 9×9 printed at full A4 or US Letter size gives you cell widths around fifteen to seventeen millimetres — wide enough for nine candidate digits in a 3×3 sub-arrangement per cell, with room to cross them out as the solve progresses. Screen-based solvers manage this with notes mode and auto-pencil marks, but the bird's-eye view of the whole grid that paper offers is genuinely hard to replicate on any display smaller than a desktop monitor.

Evil solvers also tend to develop personal conventions: which digits get circled, where in each cell a candidate sits, which colours of pencil mark a chain. None of this matters until you reach the tier where it does, and at evil it matters. A paper sheet is the canvas for those conventions. The same conventions in a digital app fight against the app's UI rather than working with it.

This page generates one fresh evil 9×9 puzzle per A4 or US Letter sheet at maximum legible cell width. Refresh for a new puzzle. Four-per-page and six-per-page evil layouts are also available for batch printing, though we expect most evil-tier solvers to prefer the single-puzzle full-page format — even an experienced solver can take a week to work through a four-puzzle evil sheet at a sustainable pace.

A caveat worth stating plainly: evil puzzles are not for everyone, and that is fine. If you find yourself fighting the puzzle rather than enjoying it, drop to master or expert — the techniques are similar, but the chains are shorter. Every evil puzzle here is uniquely solvable by logic, generated fresh on each visit, and free to print. No account, no paywall, no per-day limit. If you would rather solve on screen, the evil-sudoku player has the same generator behind it with interactive candidate notation and full undo.

A word on the 17-given minimum, because it comes up. In 2012, McGuire, Tugemann, and Civario proved through exhaustive computer search that no sudoku grid with fewer than 17 given digits can have a unique solution. That number is the theoretical floor for the puzzle as it exists. Evil grids on this site live at or one above that floor — most ship with 17 or 18 givens — which puts them in the same difficulty regime as the hardest puzzles ever published in newspaper columns or competitive solving circuits. The grids are not artificially constructed for difficulty; they are mathematically as close to the minimum as the puzzle definition permits.