Naked Singles
Learn the naked single: a cell where only one digit can possibly go. The most common move in every Sudoku solve.
A naked single is the simplest deduction in Sudoku: a cell that has exactly one candidate left, because every other digit already appears in its row, column or box. When you spot one, you can place it with certainty.
They are the backbone of every solve — even the hardest puzzle ends in a cascade of naked singles once the tricky eliminations are done. Train your eye to scan for cells hemmed in on all three sides.
Turning on pencil notes makes naked singles obvious: any cell showing a single mark is one. In the worked example below, the highlighted cell has just one remaining candidate.
Practise the Naked single
The best way to learn a technique is to use it. Play a puzzle at the level where it first appears, or drop a tricky board into the solver to watch it in action.
Frequently asked questions
What is a naked single in Sudoku?
A cell where only one digit is possible, because all the others already appear in its row, column or box. You can place that digit immediately.
How is a naked single different from a hidden single?
A naked single has one candidate in the cell. A hidden single may show several candidates, but one of its digits can go nowhere else in the unit.
More guides on the Learn hub.