Sudoku Solving Techniques
Every method you need, ordered from beginner to advanced — with a worked example for each.
How to use this guide
Sudoku techniques are tools for proving where a digit must go, or where it cannot. Learn them roughly in order: each new method only matters once the simpler ones run out. You will solve easy and medium puzzles with the first few, and reach for the rest on hard, expert and evil grids.
The techniques
1. Scanning
Cross-hatching — the first and most-used technique.
Scanning →2. Naked singles
A cell with only one candidate left.
Naked Singles →3. Hidden singles
A digit with only one home in a unit.
Hidden Singles →4. Naked pairs
Two cells, two candidates — eliminate the rest.
Naked Pairs →5. Hidden pairs
Two digits, two cells — strip everything else.
Hidden Pairs →6. Naked triples
Three cells sharing three candidates.
Naked Triples →7. Pointing pairs
Locked candidates that clear a whole line.
Pointing Pairs →8. Box-line reduction
A line that pins a digit inside one box.
Box-Line Reduction →9. X-Wing
Your first advanced eliminating pattern.
X-Wing →10. Swordfish
The X-Wing extended to three rows and columns.
Swordfish →11. XY-Wing
Three two-candidate cells that trap a digit.
XY-Wing →Beginner to advanced, in order
- Scanning (cross-hatching) — sweep rows and columns to place a digit in a box.
- Naked singles — one candidate left in a cell.
- Hidden singles — one place left for a digit in a unit.
- Naked pairs and triples — shared candidates that lock cells together.
- Pointing pairs and box-line reduction — locked candidates between a box and a line.
- X-Wing, Swordfish and chains — advanced elimination patterns for the hardest grids.
Work through them in order and practise each on a real puzzle. On Sudoku.tips, easy and medium puzzles need only the singles, hard puzzles add pairs, triples and locked candidates, expert puzzles add the X-Wing, Swordfish and XY-Wing, and evil puzzles need short chains such as coloring. Stuck on a grid? The Sudoku solver explains the next logical step.