Sudoku Strategies

A cell with only one possible candidate. The most fundamental solving technique.

A digit that can only go in one specific cell within a row, column, or box.

When a house has only one empty cell — the remaining digit is immediately placed.

Systematically remove impossible candidates using row, column, and box constraints.

Two cells in the same house share exactly two candidates — eliminate from others.

Three cells sharing exactly three candidates — eliminate those digits from the house.

Two digits that only appear in two specific cells within a house — remove other candidates.

When a candidate in a box is confined to one row or column — eliminate from that line.

A candidate appearing in exactly two cells in each of two rows/columns — rectangle elimination.

The three-row/column extension of X-Wing — eliminates candidates across three aligned lines.

Three cells forming a Y-shape pattern that allows elimination via chain logic.

Prevents multiple solutions by detecting a deadly pattern and forcing a resolution.