Easy Used from easy puzzles up.
Naked Single
A cell with one candidate left
Look at one empty cell and at its 20 neighbours: the other cells of its row, its column and its box. Every digit among them is ruled out for this cell.
When eight digits are ruled out, one candidate is left, and it goes there.
With the candidates shown, a Naked Single is a cell with a single small digit.
What to look for
Look for a cell whose row, column and box already hold eight different digits between them.
Example
- The cell it fills, with its digit in green
Practise it
In the app, Learn › Naked Single sets exercises on real positions, then a full puzzle that needs this technique and nothing harder.