Sudoku Solving Techniques
From basics to advanced, here are 15 core techniques for solving Sudoku by logic alone, complete with examples.
Basic
Naked Single
When only one candidate remains in a cell, that number is confirmed.
BasicHidden Single
Confirmed when a number can only go in one cell within a unit.
BasicFull House
When only one empty cell remains in a unit, fill it with the last number.
BasicPointing Pair
When a box's candidates for a number align in one line, remove that number from the rest of the line outside the box.
BasicClaiming (Box-Line Reduction)
When a line's candidates for a number all fall in one box, remove that number from the rest of the box.
Intermediate
Naked Pair
When two cells share the same two candidates, remove those numbers from the rest of the unit.
IntermediateHidden Pair
When two numbers can only go in the same two cells of a unit, remove the other candidates from those cells.
IntermediateNaked Triple
When three cells share a pool of three candidates, remove those numbers from the rest of the unit.
IntermediateHidden Triple
When three numbers can only go in the same three cells of a unit, remove the other candidates from those cells.
IntermediateX-Wing
A rectangle pattern where a number's candidates in two lines fall in exactly the same two cells.
Advanced
Swordfish
A fish pattern that extends the X-Wing to three lines.
AdvancedXY-Wing
Eliminates a shared number using a candidate chain between a pivot and two wing cells.
AdvancedXYZ-Wing
An extension of the XY-Wing where the pivot holds three candidates.
AdvancedSkyscraper
A single-digit chain technique that links two strong links.
AdvancedUnique Rectangle
Avoids a dangerous rectangle pattern using the uniqueness principle.