Box Brain Sudoku
Learn › Hidden Single
Easy · technique 2 of 18
Hidden Single
A digit has only one place left in a row, column or box. Also called a unique candidate.
How it works
Pick a digit and a house, then rule out every cell where that digit already appears in its row, column or box.
A worked example
Hidden single: in column 6, 4 can only go in row 7.
- The area to look at
- The cells that make the pattern
- The digit it places
A real position from a puzzle in the app. Small digits are the candidates the step looks at; coloured digits are already solved.
Practise it in Box Brain Sudoku
The app teaches Hidden Single on this same board, then hands you puzzles that need it. When you are stuck mid-game, a hint first points you to the right area, then names the technique and shows the move.