Hard Sudoku Puzzles

A puzzle is rated Hard here when its hardest required technique is Hidden Triplet, Naked Quad or Hidden Quad — verified by a solver, not guessed from a star rating. 12,846 of the 65,284 puzzles in our library are rated Hard. How our difficulty ratings work.

Hard puzzles hinge on the larger subset patterns: Hidden Triplets and Naked or Hidden Quads. Spotting four candidates locked into four cells takes disciplined pencil marks and systematic scanning, and a single missed elimination can leave you stuck for a long time.

At this tier the puzzle stops rewarding speed and starts rewarding accuracy. Hard grids turn on the larger subsets, and those patterns are only visible against a complete and correct set of candidates — one missed elimination early will hide the pattern that resolves the grid, and you will search a position that genuinely no longer contains what you are looking for.

The practical advice is to slow down at the start rather than in the middle. Get the candidates right, work one unit at a time, and when you stall, suspect your marks before you suspect your technique. If a specific pattern keeps beating you, drilling it in isolation on the practice pages is far more efficient than meeting it once per puzzle here.

Play hard puzzles

  1. Hard puzzle #1 — 24 givens · needs Naked Single, Hidden Single, Naked Pair, Omission, Hidden Pair, Hidden Triplet
  2. Hard puzzle #2 — 24 givens · needs Naked Single, Hidden Single, Naked Pair, Omission, Hidden Pair, Naked Quad
  3. Hard puzzle #3 — 24 givens · needs Naked Single, Hidden Single, Omission, Hidden Quad
  4. Hard puzzle #4 — 24 givens · needs Naked Single, Hidden Single, Omission, Naked Triplet, Hidden Pair, Hidden Triplet
  5. Hard puzzle #5 — 25 givens · needs Naked Single, Hidden Single, Omission, Naked Triplet, Hidden Pair, Naked Quad
  6. Hard puzzle #6 — 25 givens · needs Naked Single, Hidden Single, Naked Pair, Omission, Naked Triplet, Hidden Pair, Hidden Quad
  7. Hard puzzle #7 — 24 givens · needs Naked Single, Hidden Single, Omission, Naked Triplet, Hidden Triplet
  8. Hard puzzle #8 — 24 givens · needs Naked Single, Hidden Single, Omission, Hidden Pair, Naked Quad
  9. Hard puzzle #9 — 24 givens · needs Naked Single, Hidden Single, Naked Pair, Omission, Hidden Quad
  10. Hard puzzle #10 — 24 givens · needs Naked Single, Hidden Single, Omission, Hidden Triplet
  11. Hard puzzle #11 — 24 givens · needs Naked Single, Hidden Single, Naked Pair, Omission, Naked Triplet, Hidden Triplet, Naked Quad
  12. Hard puzzle #12 — 25 givens · needs Naked Single, Hidden Single, Naked Pair, Omission, Hidden Quad
Pick your own techniques instead →

Hard Sudoku FAQ

What makes a Sudoku puzzle hard?
On Precision Sudoku, difficulty is defined by the hardest technique a puzzle actually requires, verified by a solver — not by a vague star rating. A puzzle is rated Hard when the hardest move it needs is Hidden Triplet, Naked Quad, Hidden Quad.
How many hard Sudoku puzzles are there on Precision Sudoku?
12,846 of the 65,284 verified puzzles in the Precision Sudoku library are rated Hard, meaning their hardest required technique is Hidden Triplet, Naked Quad, Hidden Quad.
I have marked everything and still cannot find the move. What now?
Re-derive the candidates for one unit from scratch rather than re-scanning the whole grid. At this tier the overwhelming majority of dead ends are bookkeeping errors rather than missing knowledge, and an incorrect candidate set can hide a valid pattern completely.
Is it worth drilling techniques separately at this level?
Yes, and it is the fastest route through this tier. A Hard puzzle presents a given pattern once, which is poor practice conditions. The technique practice pages serve puzzles where a chosen pattern is the hardest required move, so you meet it repeatedly with feedback.