Expert fish
Swordfish Sudoku Strategy: Control Three Lines at Once
Swordfish extends the X-Wing idea to three rows or columns. When a digit appears in the same three positions across three lines, you can wipe that candidate from the rest of the matching columns or rows. Use Pure Sudoku to diagram it live, then lock in the elimination.
Step-by-step Swordfish
- Select a digit and mark every row where it shows up exactly twice or three times.
- Look for three rows whose candidate columns match each other (same three columns).
- Remove that digit from every other cell in those columns.
- Mirror the process by flipping rows/columns when needed.
Interactive play-by-play
Three-line Swordfish demo
Follow the animation to see three rows team up and nuke every other instance of the digit 7.
Step 1
Flag the three rows
Rows 2, 4, and 6 each contain the digit 7 in the same three columns. That’s the perfect Swordfish alignment.
Step 2
Strike the columns they cover
Every other 7 in those two columns is illegal now, so the spare notes fall away immediately.
Step 3
Place the digit or chain from the cleanup
With the junk gone, each row or column usually collapses and lets you drop the 7s in confidently.
Step 1 of 3
Finned Swordfish
Sometimes one extra candidate (the fin) sticks out. If the fin gets eliminated by another deduction, treat the remaining pattern like a standard Swordfish. Track fins with Pure Sudoku’s undo button so you can test the assumption without fear.
Training circuit
- Solve a hard puzzle until only advanced moves remain.
- Screenshot the grid, then jump into the solver sandbox to reproduce the position.
- Map every digit that appears exactly twice per row. Highlight matches.
- Record how many candidates you removed after each Swordfish.
The repetition cements muscle memory for real games, especially when the timer is running in multiplayer races.
Related guides
- X-Wing: master it first before graduating to Swordfish.
- XY-Wing: weaponize strong/weak links when fish patterns are absent.
- Pointing & claiming: prep the grid by cleaning stray candidates.