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Swordfish Technique: 3x3 Grid Pattern Explained

Master the Swordfish strategy in Sudoku. Learn how a 3x3 grid pattern across three rows and three columns eliminates candidate numbers.

Once you master X-Wing, the next natural progression is Swordfish.
While X-Wing operates on a 2x2 grid pattern (2 rows x 2 columns), Swordfish expands this logic to a 3x3 grid pattern across 3 rows and 3 columns.

Conditions for a Swordfish

A Swordfish pattern forms when:

Looking at a specific digit (e.g., 4) across 3 separate rows, the candidates for that digit are restricted to the same 3 columns (with 2 or 3 candidates per row).
These 3 rows and 3 columns form an interconnected 3x3 matrix.

Effect: You can safely eliminate candidate 4 from all other cells in those 3 columns outside the 3 Swordfish rows.

Practical Steps to Spot a Swordfish

1. Fill in complete candidate notes (Pencil Marks) across open cells.
2. Focus on rows that have only 2 or 3 candidates for a specific digit.
3. Find a trio of rows that share candidates across the exact same 3 column indices.
4. Eliminate that digit from all other cells along those 3 columns.

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