Full House

The last empty cell in a unit can only be one digit.

Learn the Full House Sudoku technique: when a row, column, or box has one empty cell, only one digit can complete it. Free, no ads.

How to use it

1. Find an almost-full unit. Look for a row, column, or 3×3 box with exactly eight digits already placed and a single empty cell.
2. Find the missing digit. List the digits 1–9 and cross off the eight already present. Exactly one remains.
3. Place it. Write the missing digit in the empty cell — it is the only value that keeps the unit valid.