Swordfish Sudoku Technique — Step-by-Step Guide
Swordfish is the next step after X-Wing. When a single digit appears in only two or three cells across three rows — and those cells share the same three columns — you can eliminate that digit from the rest of those columns.
When to look for Swordfish
Search for Swordfish only after every naked single, hidden single, naked pair and X-Wing has been resolved. The pattern depends on full pencil marks across the whole grid.
Spotting the pattern
Pick a candidate digit. Scan the rows where that digit has exactly 2 or 3 positions. If three such rows together touch only three columns, you have a Swordfish — remove the digit from those three columns outside the three rows.
Common mistakes
Swordfish also works the other way: three columns touching only three rows. Don't confuse it with Jellyfish (4×4) or with three unrelated X-Wings. Always check that the same three columns appear in all three rows before eliminating.
Frequently asked
Is Swordfish harder than X-Wing?
Conceptually no, but visually yes — three lines are harder to track than two. Full pencil marks make it spottable.
How often does Swordfish appear?
Roughly once every 8–12 hard puzzles, and almost every expert puzzle.