What is Swordfish in Sudoku?
Swordfish is a candidate pattern spanning three rows and three columns that enables eliminations along the intersecting lines.
Pure Sudoku
Advanced technique
Swordfish extends fish logic across three lines.
Swordfish restricts one candidate across three rows and the same three columns. Those locked positions remove the candidate from other cells in the intersecting columns.
- Level
- Advanced
- Pattern
- Three rows restrict a candidate to three columns
- Outcome
- Logical progress
Focused example
Candidate 7 is restricted across three matching lines.
The highlighted cells show the exact scope of the pattern. Read the candidates before making an elimination.
How it works
Apply the pattern in four checks.
- Choose one candidate and map its possible cells across several rows.
- Find three rows whose candidates occupy only the same three columns.
- Confirm each selected row contains two or three of those candidate positions.
- Remove the candidate from other cells in the three columns.
Know the difference
Use the pattern only when every condition is true.
X-Wing uses two rows and two columns. Swordfish applies the same restriction across three rows and three columns.
After the move, re-scan the affected unit for singles before searching for another advanced pattern.
Common mistake
Protect the logic before erasing a candidate.
The pattern can use fewer than nine corner positions, but every selected candidate must remain inside the same three intersecting lines.
If any required condition is missing, leave the candidates in place and continue scanning.
Continue playing
Choose your next Sudoku route.
FAQ
Quick answers before you play.
Is Swordfish harder than X-Wing?
It is usually harder to spot because it uses three lines and does not need every intersection to contain the candidate.
Should I search every digit for Swordfish?
Search only after simpler techniques stall and candidate notes are complete.
Practice loop
Find it on a live board.
Pause when the board slows down, check the candidate conditions, make one justified move, and scan again.