Sudoku techniques
Eight techniques solve every puzzle on GridPorch, and each level adds two more. Every guide walks through a real example, one step at a time.
Easy
Every easy puzzle can be finished with these two alone.
Naked single
A cell where every number but one is already taken.
Hidden single
The only place left for a number in its row, column or box.
Medium
Medium puzzles add these patterns, and pencil marks start to matter.
Naked pair
Two cells share the same two candidates, so nothing else in their group can use those numbers.
Pointing pair
Within a box, a number is confined to one line, so the rest of that line can't use it.
Hard
These are harder to see, because extra candidates hide them.
Hidden pair
Two numbers that can only go in the same two cells.
Box-line reduction
Within a line, a number is confined to one box, so the rest of that box can't use it.
Expert
Fish patterns reach across the whole board, one number at a time.
Haven't played before? Start with how to play sudoku.