---
title: "Hidden Quad: Sudoku Technique #14 | Sudoku Flow"
description: "Hidden Quad: Four numbers whose candidates together appear in only four cells of a row, column, or box claim those cells for themselves."
url: https://sudokuflow.com/lessons/hiddenQuad/
language: en
---

[Sudoku technique lessons](https://sudokuflow.com/lessons/) / Hidden Quad

Lesson 14

# Hidden Quad

## The rule

Four numbers whose candidates together appear in only four cells of a row, column, or box claim those cells for themselves.

## Step by step

1. In this row, 1, 2, 3, 4 appear as candidates only in these four cells.
2. These four cells must contain 1, 2, 3, 4 among them, so we can remove any other candidates from those cells.

[Read the full lesson, with more examples →](https://sudoku.rubigogames.com/techniques/hidden-quad.html)

In our app, when this technique is the next step, the hint names it and shows you why, step by step. No ads, free to download.

[App Store iPhone, iPad, Mac](https://apps.apple.com/app/apple-store/id6502922368?pt=125379530&ct=sudokuflow_cta&mt=8) [Google Play Android](https://play.google.com/store/apps/details?id=com.rubigogames.sudoku&referrer=utm_source%3Dsudokuflow%26utm_medium%3Dcta%26utm_campaign%3Dlesson)

## Try it on more boards

Each board is a real puzzle from our app, at a moment where Hidden Quad applies. Find the step yourself, or tap Hint and the app's own hint walks you through it.

Hidden Quad practice board:

```text
.  8* 1* | .  7  9* | 3* 2  .
7* 9* 6  | 2  4  3  | 5  .  .
3  2  .  | .  1  8  | .  .  .
---------+----------+---------
8  5* 7  | 3* 6* 1  | .  4  .
1  .  .  | 9  2  5  | .  .  .
9* .  2* | 7* 8* 4  | 1* .  .
---------+----------+---------
.  1  .  | 8  .  .  | 4  7  .
.  .  8* | .  .  7* | 6  .  .
.  7  9  | .  5* .  | .  3  .
```
Digits marked * were filled in by a player; the others were printed with the puzzle.

![Sudoku app icon](https://sudokuflow.com/assets/app-icon.png)

## Want more boards like this?

We also make a Sudoku app for iPhone, iPad, Mac and Android. There are no ads in it at all, it works offline, and when you ask for a hint it shows you the technique instead of just filling in a number.

[App Store iPhone, iPad, Mac](https://apps.apple.com/app/apple-store/id6502922368?pt=125379530&ct=sudokuflow_web&mt=8) [Google Play Android](https://play.google.com/store/apps/details?id=com.rubigogames.sudoku&referrer=utm_source%3Dsudokuflow%26utm_medium%3Dweb%26utm_campaign%3Dsite)

Sudoku Flow is made by Rubigo Games, the developer of the Sudoku app recommended on this site.