An extension of the X-Wing pattern to three rows and three columns. Essential for cracking hard and expert Sudoku puzzles.
A Swordfish pattern occurs when you focus on a single candidate number and find three rows where that candidate appears in at most three cells per row, and the columns occupied by those cells collectively cover exactly three columns. The candidate must be placed once in each of those three rows, and those placements will occupy three of the column positions - meaning no other cell in those three columns can hold that candidate.
Unlike the X-Wing, where each base row must have exactly two candidate positions, a Swordfish row can have two or three positions. The critical requirement is that the total number of distinct columns used across all three rows is exactly three. This makes the pattern harder to spot but potentially more powerful in terms of eliminations.
The Swordfish belongs to the "fish" family of techniques - a generalization of the X-Wing concept. Understanding this family of patterns is key to advancing your solving skills. It extends upward to the Jellyfish (four rows, four columns). For definitions of key terms, visit our Sudoku glossary.
The Swordfish should only be attempted after all intermediate techniques have been exhausted. If Naked Pairs, Hidden Pairs, Pointing Pairs, Box-Line Reduction, and X-Wings have not resolved the puzzle, it is time to look for Swordfish patterns.
Swordfish patterns appear primarily in hard and expert-level puzzles. They are rare in medium puzzles and essentially non-existent in easy ones. For a complete progression of techniques, visit our strategy guide or review how to play Sudoku.
Swordfish is classified as an advanced-level technique, bordering on expert. It is significantly harder to spot than the X-Wing and requires careful, systematic analysis of candidate distributions.
Never needed - basic techniques are sufficient
Extremely rare - intermediate techniques handle these
Occasionally needed when X-Wings are insufficient
Important technique - part of the advanced solver toolkit
A Swordfish is an advanced elimination technique that extends the X-Wing concept to three rows and three columns. When a candidate number appears in at most three positions in each of three rows, and those positions collectively span exactly three columns, the candidate can be eliminated from all other cells in those three columns.
An X-Wing uses two rows and two columns forming a rectangle. A Swordfish uses three rows and three columns. In a Swordfish, the candidate does not need to appear in exactly two cells per row - it can appear in two or three cells per row, as long as the total column coverage is exactly three columns.
Swordfish patterns are relatively rare compared to X-Wings. They typically appear in hard and expert-level puzzles. Many solvers go through dozens of puzzles before encountering one. When they do appear, however, they often break open an otherwise stuck puzzle.
Yes, exactly like the X-Wing, the Swordfish works symmetrically. You can define it using three columns as the base lines, with the covering lines being three rows. The elimination logic is identical - just swap rows and columns throughout the process.
Always exhaust simpler techniques first: Naked Singles, Hidden Singles, Naked Pairs, Pointing Pairs, Box-Line Reduction, and X-Wings. Swordfish is a last-resort technique for situations where all simpler methods have stalled.
Track digit 5. Each marked cell shows where 5 could go. Look for three rows where 5 fits in only the same set of columns.
Step 1 of 4 — full interactive demo available with JavaScript enabled
Ready to put your skills to the test?
Try Final Sudoku - an ad-free Sudoku experience with smart tools