Swordfish + Hidden Pair Sudoku Puzzles

Every puzzle below has Swordfish and Hidden Pair as its two hardest required moves, verified by a solver — 3,084 of the 65,284 puzzles in our library match. Rusty on either one? Drill them separately first: Swordfish practice · Hidden Pair practice.

Why these two appear together

A Swordfish needs a digit whose possible positions across three lines fall entirely within three columns. That is a demanding containment condition, and on most grids it is not satisfied until something else has pruned the candidates. Here that something is a Hidden Pair.

The Hidden Pair works inward: two digits that can only live in the same two cells of a unit let you delete every other candidate from those two cells. Those deletions do not just tidy the unit — they remove possible positions for other digits from the lines running through it, which is exactly what tightens a digit's footprint enough for a three-line fish to exist.

So the sequence on these puzzles runs from the local and cheap to the global and expensive, and reversing it wastes the search. It is also a good reminder that a Swordfish is never the move you open with.

Curated Swordfish + Hidden Pair puzzles

  1. Practice puzzle #1 — 25 givens · needs Naked Single, Hidden Single, Hidden Pair, Swordfish
  2. Practice puzzle #2 — 28 givens · needs Naked Single, Hidden Single, Hidden Pair, Swordfish
  3. Practice puzzle #3 — 25 givens · needs Naked Single, Hidden Single, Hidden Pair, Swordfish
  4. Practice puzzle #4 — 25 givens · needs Naked Single, Hidden Single, Hidden Pair, Swordfish
  5. Practice puzzle #5 — 23 givens · needs Naked Single, Hidden Single, Hidden Pair, Swordfish
  6. Practice puzzle #6 — 25 givens · needs Naked Single, Hidden Single, Hidden Pair, Swordfish
  7. Practice puzzle #7 — 26 givens · needs Naked Single, Hidden Single, Hidden Pair, Swordfish
  8. Practice puzzle #8 — 24 givens · needs Naked Single, Hidden Single, Hidden Pair, Swordfish
  9. Practice puzzle #9 — 27 givens · needs Naked Single, Hidden Single, Hidden Pair, Swordfish
  10. Practice puzzle #10 — 25 givens · needs Naked Single, Hidden Single, Hidden Pair, Swordfish
  11. Practice puzzle #11 — 25 givens · needs Naked Single, Hidden Single, Hidden Pair, Swordfish
  12. Practice puzzle #12 — 23 givens · needs Naked Single, Hidden Single, Hidden Pair, Swordfish
Get a fresh Swordfish + Hidden Pair puzzle →

Swordfish + Hidden Pair FAQ

How many Sudoku puzzles combine Swordfish and Hidden Pair?
3,084 puzzles in the Precision Sudoku library have Swordfish and Hidden Pair as their two hardest required techniques (beyond singles), out of a library of 65,284 solver-verified puzzles.
Why can I not find the Swordfish at the start of these puzzles?
Because it is not there yet. The containment condition — a digit restricted to three columns across three rows — usually only becomes true after the Hidden Pair's eliminations remove competing positions from the lines involved.
Does the Hidden Pair always come before the Swordfish?
In these curated puzzles, yes, and it reflects the general rule. Inward-pruning unit techniques create the reduced candidate counts that grid-spanning patterns require, so the cheap local move is nearly always the enabler rather than the obstacle.