Sudoku Strategies, Explained with Diagrams
Most people learn Sudoku by scanning for obvious numbers, then hit a wall on harder boards and assume they need to guess. They don't. Every standard Sudoku is solvable by pure logic — you just need a bigger toolbox. This guide walks through the eight techniques that carry you from beginner to confident solver, each one explained with a worked diagram you can read at a glance.
The strategies build on each other. The first three place digits directly and need no notes. The next five work on pencil marks — the small candidate numbers you jot into empty cells — and clear those candidates away until placements appear. Learn them in order and each new technique will feel like a natural extension of the last.
If you want a board to practise on while you read, open Sudoku Zen in another tab. Its notes mode lets you pencil-mark candidates exactly as the diagrams below show. Brand new to the game? Start with how to solve Sudoku for beginners first, then come back here.
The eight techniques
- Beginner
Last Remaining Cell
The single missing digit in an almost-full row, column, or box.
- Beginner
Hidden Singles
A digit with only one legal home in a unit — even when the cell looks busy.
- Beginner
Cross-Hatching
Scan rows and columns to place a digit inside a box.
- Intermediate
Naked Pairs
Two cells sharing the same two candidates lock those digits in.
- Intermediate
Hidden Pairs
Two digits confined to two cells clear everything else out of them.
- Intermediate
Naked Triples
Three cells, three candidates — and the quads that follow.
- Intermediate
Pointing Pairs
A digit trapped on one line of a box points down that line.
- Intermediate
Box/Line Reduction
The reverse: a line confines a digit to a single box.
How the techniques fit together
Beginner techniques — last remaining cell, hidden singles, and cross-hatching — are about placing digits. They finish easy boards on their own and get you most of the way through a medium one. None of them require notes; you do them by looking.
Intermediate techniques are about eliminating candidates so that a placement becomes possible. Naked and hidden pairs, naked triples, pointing pairs, and box/line reduction never put a number on the board by themselves. Instead they shave possibilities off other cells until a hidden single or last remaining cell appears. That two-step rhythm — eliminate, then place — is the whole game at the intermediate level.
Once these are reflexive, the advanced patterns (X-Wing, Swordfish, XY-Wing) are just the same idea stretched across several rows and columns at once. We'll cover those in a follow-up guide. For now, master the eight below and you'll solve the vast majority of "hard"-rated puzzles without ever guessing.
A note on guessing
You may have seen "guess and check" listed as a Sudoku method. It works, but it isn't solving — it's brute force, and on a contaminated board it's hard to undo. Every technique in this guide is deductive: each move is forced by the rules, so you can always explain why a digit goes where it does. That's the difference between finishing a puzzle and actually getting better at them. Play Sudoku Zen — six difficulties