---
title: "Jellyfish: Four lines form one pattern"
description: "A Jellyfish confines a digit’s candidates in four rows to four columns. Learn how this pattern rules out candidates outside those starting rows."
lang: "en"
canonical: "https://unisu-sudoku.app/en/sudoku-techniques/jellyfish/"
---

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

Advanced techniques

# Jellyfish: Four lines form one pattern

A Jellyfish confines a digit’s candidates from four starting rows to exactly four columns. Those columns are needed for the four placements, allowing eliminations outside the starting rows.

![Unisu lesson on Jellyfish, showing the explained grid](https://unisu-sudoku.app/_astro/en.C1SC0k4P_4x9nb.webp)

A Jellyfish confines a digit’s candidates from four starting rows to exactly four columns. Those columns are needed for the four placements, allowing eliminations outside the starting rows.

## An example from the app

In row 2, row 5, row 7, row 9, candidate 9 is confined to column A, column F, column B, column H. There are 4 starting lines and exactly 4 crossing lines.

The 4 required placements of 9 occupy column A, column F, column B, column H. In those lines, 9 is ruled out outside row 2, row 5, row 7, row 9.

These notes are therefore ruled out: A1: 9; A8: 9; F8: 9; H1: 9; H8: 9.

The image shows the candidates relevant to this step. A note being hidden does not mean it has been logically eliminated.

## Practice the next step

Not every corner of a large rectangle needs a candidate. Check the complete positions in all four starting rows.

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 Jellyfish

### What are the four starting areas?

Four rows or four columns whose possible positions for one digit are together restricted to four cover areas.

### Must each starting area contain four candidates?

No. Individual areas can have fewer positions. Their combined restriction to four cover areas is what matters.

### What if another position lies outside the cover areas?

This Jellyfish condition is not satisfied. You must not overlook an additional actual candidate.

### Where can I eliminate the digit?

In the four cover areas outside the starting areas. The direction depends on whether you began with rows or columns.

### Should I always look for Jellyfish first?

Check simpler steps, X-Wing and Swordfish first. Tracking four areas needs complete, current candidates.

## 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

### Swordfish

[Read more: Swordfish](https://unisu-sudoku.app/en/sudoku-techniques/swordfish/)

## Where to go next

Advanced techniques

Unisu · Oct 27, 2026

### [Finned X-Wing: An X-Wing with an extra possibility](https://unisu-sudoku.app/en/sudoku-techniques/finned-x-wing/)

A Finned X-Wing adds a fin to the basic pattern. Remove only candidates that conflict with both the fin and the X-Wing left when the fin is false.

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)