Sudoku Solving Techniques: The Intermediate Toolkit
Naked singles and cross-hatching get you through easy puzzles. Medium and hard puzzles need a real toolkit. These are the sudoku solving techniques that unlock most stuck grids — in the order you should learn them.
Before any of these techniques are useful, you need to be marking candidates. Don't pencil-mark every cell — mark only the cells that have 2 or 3 candidates after a full scan. That's the minimum data these techniques need to fire.
1. Naked Pairs
When two cells in the same row, column, or box both contain exactly the same two candidates — say {4, 7} — those two digits must occupy those two cells. You can eliminate 4 and 7 from every other cell in that unit. Naked pairs are the highest ROI technique you can learn after basics.
2. Naked Triples (and Quads)
The same logic extends to three cells sharing three candidates ({2, 5, 8}, {2, 5}, {5, 8} all in one row). Those three digits are locked into those three cells. Eliminate from everywhere else in the row. Quads work the same way but are rarer.
3. Hidden Pairs
A hidden pair is when two digits can only appear in two specific cells of a unit — even though those cells may also contain other candidates. If 3 and 9 in box 4 can only go in cells R5C2 and R6C3, you can erase every other candidate from those two cells. Hidden pairs are easy to miss; train the eye to scan unit-by-unit, digit-by-digit.
4. Hidden Triples
Three digits restricted to three cells in a unit (each cell can contain a subset). Strip all other candidates from those cells. Mechanically identical to naked triples, but the lock is on the digits rather than the cells.
5. Pointing Pairs (and Triples)
If a digit's only candidates inside a 3×3 box all sit in the same row or column, that digit must come from one of those cells — so you can eliminate it from the rest of that row or column outside the box. This is one of the most common ways to break a stalled puzzle.
6. Box/Line Reduction
The reverse of pointing pairs. If a digit's only candidates in a row or column all fall inside one 3×3 box, that digit must come from those cells — eliminate it from the rest of the box. Pairing this with pointing pairs solves most "stuck" medium and hard puzzles without going further.
7. Y-Wing
A simpler advanced technique that's still in the intermediate toolkit. Three cells with two candidates each ({A,B}, {A,C},{B,C}) where the "pivot" cell sees both others. The candidate C can be eliminated from any cell that sees both wing cells. Worth learning before X-wing.
When to use which
A reliable order for medium-hard puzzles:
- Finish all naked and hidden singles first
- Pencil-mark only stalled cells
- Scan for naked pairs, then hidden pairs
- Apply pointing pairs and box/line reduction
- If still stuck, try a Y-wing
If none of these work, you've reached genuinely hard territory. See how to solve hard sudoku for X-wing, swordfish, and XY-chain methods.
Drill, then apply
Reading techniques without using them is the slowest way to improve. Drill in solo mode on medium puzzles until naked pairs and pointing pairs come automatically — then take them into ranked matches.