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Naked Singles

In sudoku, a Naked Single occurs when you examine a cell's remaining candidates — the digits not yet excluded by the row, column and box — and find exactly one possibility. That lone candidate is the naked single: the only digit that can legally occupy the cell. Finding naked singles is one of the most rewarding moments in sudoku solving because each one represents a guaranteed, logic-backed placement.

Spotting naked singles

Naked singles become visible only after you have filled in notes across your sudoku board. Scan the grid systematically — cell by cell, row by row. Any cell displaying a single candidate number is a naked single. You can place that digit immediately with 100% confidence. On Sudoked.com, the hint feature can point out naked singles when you get stuck, explaining exactly why the highlighted cell must contain the indicated digit. Developing the habit of scanning your notes for lone candidates is the single most effective way to improve your sudoku solving speed and accuracy.

The simplest advanced move

Each time you place a naked single on the sudoku grid, you remove that digit as a candidate from every other cell in the same row, column and box. This cascading effect often creates new naked singles in neighboring cells. A typical solve on a medium or hard sudoku puzzle unfolds as a chain reaction: spot a naked single, place it, update the notes, and immediately find another. This cascade is the hallmark of smooth, confident sudoku solving. Advanced players learn to anticipate these chains, planning several naked singles ahead of their current placement.

Build the chain

It is useful to understand the difference between naked and hidden singles, even though both result in placing a digit. A naked single is visible directly in the cell's notes — you see only one candidate. A hidden single is a digit that appears as a candidate in multiple cells within a house, but in only one cell within that house. The digit is "hidden" among other candidates. Naked singles are easier to spot once notes are filled, which is why beginners are advised to master notes and naked singles before moving to hidden singles, pairs, triplets and the larger sudoku technique family.

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