The Hardest Jigsaw Puzzles, and What Actually Makes One Hard

Difficulty is almost always sold as piece count. It is a convenient measure and a mostly wrong one. A 32,000-piece puzzle is chiefly long. Hard is a different property.

What actually makes a puzzle hard

Repetition without landmarks. A single-colour puzzle removes every clue except shape. You are no longer solving a picture; you are sorting geometry.

Uniform texture. Shingle beaches, foliage, crowds, star fields. The image gives you colour but no orientation.

Irregular cutting. With whimsy pieces and varying shapes, experience stops helping, because you can no longer predict what an edge will look like.

Double-sided printing. This does not double the work, it roughly quadruples it: every piece has two candidate images and two orientations.

No straight edge. Remove the border and you remove the scaffold every other technique is built on.

The famous ones

• "Impossible" puzzles built on a repeating pattern — hard by withholding information.
• All-white and all-black editions, which are pure shape work.
• Round and free-form puzzles, where the edge no longer helps because it has no corners.
• Very large sets, 18,000 pieces and up — mostly a test of floor space, time and persistence.

How hard is a photo puzzle?

With a personal photograph, the image decides, not the count. A group photo with distinct blocks of colour is comfortable at 500 pieces. A landscape that is half sky is tougher at 252 than the number suggests.

Want it harder: lots of sky, water, repeated pattern. Want it kinder: faces large, colours separated, little uniform area. When you upload a photo you can see which counts your image supports, 30 up to 1,000, and choose how hard the evening should be. There is more on this in best photos for a jigsaw puzzle.

One honest note

Very hard puzzles are given more often than they are finished. If you are buying one as a gift, ask whether that person wants a challenge or wants to switch off. Those are two different presents.