---
title: "Hidden Single: One place left for a digit"
description: "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."
lang: "en"
canonical: "https://unisu-sudoku.app/en/sudoku-techniques/hidden-single/"
---

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

Fundamentals

# Hidden Single: One place left for a digit

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 lesson on Hidden Single, showing the explained grid](https://unisu-sudoku.app/_astro/en.DU6OoR18_2wc4B.webp)

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.

## An example from the app

This 3×3 box is missing 3 and 5. Both are candidates for its top-left cell. We will now check where the 5 can go in this box.

The highlighted large 5 is already in the column of the other empty cell. In this box, 5 can therefore go only in the top-left cell.

## Practice the next step

Track that digit throughout the whole area. This differs from looking for a cell with only one candidate.

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 Hidden Single

### Why is it hidden if the cell contains several notes?

The digit has only this position in the area. The cell’s other notes merely conceal that unique position.

### Where should I count a digit’s positions?

Across a complete row, column or box. An arbitrary fragment of the grid is not sufficient.

### Do I need every candidate in that area?

You must consider every actual position of the digit. Overlooking one can create a false Hidden Single.

### How is it different from Naked Single?

Naked Single gives a cell one possible digit. Hidden Single gives a digit one possible position in an area.

### What if the digit can still occupy two cells?

It is not a Hidden Single in that area. Check other areas or other candidate relationships.

## 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

### Naked Single

[Read more: Naked Single](https://unisu-sudoku.app/en/sudoku-techniques/naked-single/)

## Where to go next

Core techniques

Unisu · Oct 27, 2026

### [Locked Candidates: Use the overlap between a box and a line](https://unisu-sudoku.app/en/sudoku-techniques/locked-candidates/)

Locked Candidates: when all candidates for a digit in a box lie on one row or column, remove that digit from the rest of that line outside the box.

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)