Swordfish + X-Wing Sudoku Puzzles

Every puzzle below has Swordfish and X-Wing as its two hardest required moves, verified by a solver — 2,180 of the 65,284 puzzles in our library match. Rusty on either one? Drill them separately first: Swordfish practice · X-Wing practice.

Why these two appear together

This pairing is the same argument at two sizes in one grid, which makes it the best available test of whether you understand fish rather than recognise them. An X-Wing confines a digit to two lines crossing two others; a Swordfish does it with three and three. Every X-Wing is really a degenerate Swordfish, and a solver who has learned both as pictures rather than as a containment rule will often find the larger pattern while walking straight past the smaller one.

The order to work them in is the cheap one first. Always test whether a digit has exactly two homes in two lines before committing to the three-line search, because the X-Wing's eliminations frequently dismantle the position that the Swordfish was going to resolve. Finding a valid Swordfish that an X-Wing would have handled is not a mistake exactly, but it is a great deal of work for the same result.

Curated Swordfish + X-Wing puzzles

  1. Practice puzzle #1 — 24 givens · needs Naked Single, Hidden Single, X-Wing, Swordfish
  2. Practice puzzle #2 — 26 givens · needs Naked Single, Hidden Single, X-Wing, Swordfish
  3. Practice puzzle #3 — 25 givens · needs Naked Single, Hidden Single, X-Wing, Swordfish
  4. Practice puzzle #4 — 25 givens · needs Naked Single, Hidden Single, X-Wing, Swordfish
  5. Practice puzzle #5 — 25 givens · needs Naked Single, Hidden Single, X-Wing, Swordfish
  6. Practice puzzle #6 — 26 givens · needs Naked Single, Hidden Single, X-Wing, Swordfish
  7. Practice puzzle #7 — 24 givens · needs Naked Single, Hidden Single, X-Wing, Swordfish
  8. Practice puzzle #8 — 25 givens · needs Naked Single, Hidden Single, X-Wing, Swordfish
  9. Practice puzzle #9 — 25 givens · needs Naked Single, Hidden Single, X-Wing, Swordfish
  10. Practice puzzle #10 — 26 givens · needs Naked Single, Hidden Single, X-Wing, Swordfish
  11. Practice puzzle #11 — 26 givens · needs Naked Single, Hidden Single, X-Wing, Swordfish
  12. Practice puzzle #12 — 24 givens · needs Naked Single, Hidden Single, X-Wing, Swordfish
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Swordfish + X-Wing FAQ

How many Sudoku puzzles combine Swordfish and X-Wing?
2,180 puzzles in the Precision Sudoku library have Swordfish and X-Wing as their two hardest required techniques (beyond singles), out of a library of 65,284 solver-verified puzzles.
If I find a Swordfish, could an X-Wing have solved it more cheaply?
Often, yes. Because both rest on the same containment argument, positions that admit a Swordfish frequently admit a smaller fish on the same digit. Check for two-line patterns before starting a three-line search — the eliminations are usually identical and cost far less to find.
Why do these two techniques appear together so often?
Because they need the same conditions. Both require a digit whose possible positions have already been squeezed into very few cells per line, so a grid that produces one has usually produced the raw material for the other on a different digit.