Hidden Quad Walkthrough

A Hidden Quad is four digits that appear only within the same four cells of a unit. Those cells are reserved for those digits, so other candidates can be cleared from them.

Sudoku board with pencil-mark candidates before applying the Hidden Quad technique — Before — candidates pencilled in. There is a Hidden Quad in Row 3.

There is a Hidden Quad in Row 3. Applying the Hidden Quad eliminates 4 candidates (struck out in red below; any solved cells shown in green).

The same Sudoku board after the Hidden Quad technique eliminates 4 candidates — After applying the Hidden Quad.

Learn the Hidden Quad technique →Practice it on a real puzzle →