Sudoku technique library
Learn Sudoku techniques one pattern at a time.
Start with basic singles, then build toward pairs, triples, X-Wing, Swordfish, and chain patterns. Each page gives you one concrete board example before sending you back to practice in Sudoku Coach.
Beginner
Single Candidate in Sudoku: How to Spot It
Learn the Single Candidate Sudoku technique: check one cell's row, column, and box until only one legal number remains.
Hidden Single in Sudoku: How to Spot It
Learn the Hidden Single Sudoku technique: when a number has only one possible position in a row, column, or box.
Candidate Notes in Sudoku: How to Use Them
Learn how to write and maintain Sudoku candidate notes so every later technique has reliable evidence.
Intermediate
Locked Candidates in Sudoku: How to Spot Them
Learn the Locked Candidates Sudoku technique: when candidates are trapped in one line or one box and can be removed elsewhere.
Naked Pair in Sudoku: How to Spot It
Learn how Naked Pairs work in Sudoku, when to look for them, and how to remove candidates safely.
Hidden Pair in Sudoku: How to Spot It
Learn how Hidden Pairs work in Sudoku, why they are harder to see than Naked Pairs, and how to clean up candidates.
Advanced
Naked Triple in Sudoku: How to Spot It
Learn the Naked Triple Sudoku technique: three cells in one unit reserve three candidates, allowing eliminations from the rest of that unit.
Hidden Triple in Sudoku: How to Spot It
Learn the Hidden Triple Sudoku technique: three numbers are limited to three cells, so extra candidates inside those cells can be removed.
X-Wing in Sudoku: How to Spot It
Learn the X-Wing Sudoku technique with a simple candidate pattern, clear elimination rule, and practice-focused explanation.
XY-Wing in Sudoku: How to Spot It
Learn the XY-Wing Sudoku technique: a pivot cell and two wing cells force a shared candidate elimination.
Expert
Swordfish in Sudoku: How to Spot It
Learn the Swordfish Sudoku technique: three rows and three columns lock a candidate into a fish pattern.
XY-Chain in Sudoku: How to Spot It
Learn the XY-Chain Sudoku technique: linked bivalue cells prove a candidate cannot stay in a cell that sees both chain ends.
Turn reading into practice
Technique pages explain the pattern. Sudoku Coach helps you recognize it on real boards.