---
title: "Naked Single: One candidate left in a cell"
description: "A Naked Single is a cell with exactly one candidate remaining. Its row, column and box rule out every other digit."
lang: "en"
canonical: "https://unisu-sudoku.app/en/sudoku-techniques/naked-single/"
---

[Back to the learning guides](https://unisu-sudoku.app/en/learn/)

Fundamentals

# Naked Single: One candidate left in a cell

A Naked Single is a cell with exactly one candidate remaining. Its row, column and box rule out every other digit.

![Unisu lesson on Naked Single, showing the explained grid](https://unisu-sudoku.app/_astro/en.DBM9z_ki_ZDrUnx.webp)

A Naked Single is a cell with exactly one candidate remaining. Its row, column and box rule out every other digit.

## An example from the app

The highlighted row is missing 3 and 5. Looking only at this row, either could go in its top-left empty cell.

Now check the column of that cell: it already contains 3. Only 5 fits the cell. The small 5 records this checked result — a Naked Single.

## Practice the next step

The cell’s candidate list must be complete. Forgetting a note does not turn two possibilities into a single.

In the app, follow the reasoning in the matching lesson and try a task yourself. With a new puzzle, always start from its actual candidate state.

## Questions about Naked Single

### When is a cell a Naked Single?

When exactly one digit remains possible. Check the cell’s row, column and box together.

### Is it the same as Hidden Single?

No. Naked Single examines a cell’s candidates. Hidden Single examines a digit’s possible positions within an area.

### Does one visible note prove a Naked Single?

Only if the candidate list is complete and current. A forgotten possibility does not make the cell unique.

### What should I check after placing it?

Update its row, column and box. The new digit can rule out further candidates there.

### What if there is no Naked Single?

Look for Hidden Single or another suitable pattern. Having several possibilities is not a reason to guess one.

## Keep practicing in Unisu

Download Unisu for iPhone or Android. Solve a puzzle or work through a guided lesson on the technique.

-   [Download on the App Store](https://apps.apple.com/us/app/id6775824061?l=en)
-   [Get it on Google Play](https://play.google.com/store/apps/details?id=app.unisu.sudoku&hl=en)

## Useful before this guide

### Sudoku pencil marks: track and update candidates

[Read more: Sudoku pencil marks: track and update candidates](https://unisu-sudoku.app/en/sudoku-techniques/pencil-marks/)

## Where to go next

Fundamentals

Unisu · Oct 27, 2026

### [Hidden Single: One place left for a digit](https://unisu-sudoku.app/en/sudoku-techniques/hidden-single/)

A Hidden Single occurs when a digit has only one possible place in a row, column or box. The cell itself can still have other candidates.

Unisu

### [Learn Sudoku: a path from rules to techniques – Unisu](https://unisu-sudoku.app/en/learn/)

Start with the rules, get comfortable with pencil marks and choose a technique for the situation you’re working on.

Download app

## Ready for a puzzle? Take a moment.

Download Unisu on your phone. Start a Sudoku or choose a lesson on the technique you want to understand.

-   [Download on the App Store](https://apps.apple.com/us/app/id6775824061?l=en)
-   [Get it on Google Play](https://play.google.com/store/apps/details?id=app.unisu.sudoku&hl=en)

![The daily challenge in Unisu](https://unisu-sudoku.app/_astro/en.C-sYR9hJ_1QwI9G.webp)

![A classic Sudoku game in Unisu](https://unisu-sudoku.app/_astro/en.C6DJ1kiE_2dRWDN.webp)