Printable Nightmare Sudoku (PDF)

Updated 23 August 2026

Nightmare holds just 25 clues, and it is the booklet where the printed page genuinely earns its keep. Every puzzle in it was tested against a solver that already knows every fish and wing — including the swordfish and the XY-Wing — and kept only because that solver stalled. What finishes them is chain reasoning, and a chain is far easier to build on paper, where you can pencil the links in and follow them, than on a cramped screen. Our sample of 40 boards measures the tier at SE 4.5 to 7.3.

What is inside the booklet

The 16 puzzles print 4 to a page, sized so a chain crossing the whole grid still fits comfortably on one sheet. Full solved grids close the booklet, which matters more here than at the easier tiers — a single missed elimination partway along a chain compounds quickly, and a printed answer key catches it. The measured spread behind these claims lives in the sudoku difficulty rating guide.

Why paper helps with chains

A chain has no fixed shape: it is built link by link, and the only way to keep track of it is to write it down. On paper you can mark each strong and weak link as you go, follow the alternation to the far end, and see immediately which cells both ends can see. That is genuinely awkward on a phone screen you have to scroll. It is also the booklet where a wrong elimination compounds worst: mark a candidate as gone that should have stayed, and every link after it is unsound, so treat the solution pages as a real checkpoint rather than a formality.

Where to go next

Chains falling into place? The printable Hell sudoku booklet is the last tier, built from a verified 17-clue corpus. Step back to printable Hard sudoku for fish and wings only, or play Nightmare on a screen at the Nightmare sudoku lander.