How to use Jackett with Sonarr

Introduction

From the official Jackett app github:

Jackett works as a proxy server: it translates queries from apps (Sonarr, Radarr, SickRage, CouchPotato, Mylar, Lidarr, DuckieTV, qBittorrent, Nefarious etc) into tracker-site-specific http queries, parses the html response, then sends results back to the requesting software. This allows for getting recent uploads (like RSS) and performing searches. Jackett is a single repository of maintained indexer scraping & translation logic - removing the burden from other apps.

In this guide, we will be using Jackett for scraping torrents into Sonarr app

Installation

Go to your client area, click the Installable Apps section and add both applications via +Add Application button. You can find a more detailed guide regarding 1-click installation of the apps here

Jackett

Click Go to Application and a new window will be opened. After your successful login, then main page of the Jackett app will appear. On the top right corner you can find your API Key that will be needed afterwards

1) Click +Add indexer to add your indexer of your choice

Note: The API Key credential shown at the screenshot is temporary and used only for this guide. Your key will -obviously- differ than the one shown here.

2) Let's say we want to use Torrentz2 . Scroll downwards and click the wrench icon at the right section.

This will open up the settings of that indexer. Write somewhere down the codes for the categories you are interested in as Sonarr needs manual input of the codes (e.g. 2040 for Movies/HD, 5000 for TV etc). Alternatively, you can click the wrench icon of the indexer once you add it, so you can see at a later state the codes you will be needing.
Press Okay button afterwards to add the indexer.

Your will be automatically navigated to Jackett's main screen where you can see that the indexer was successfully added.

NOTE: Don't close the window yet, as it will be needed later for the API Key and URL field at the Sickchill app

Sonarr

Assuming you have being already using the Sonarr app, this guide will only show how to add and use the custom indexer. However, if you are new here, there is an excellent guide regarding the installation and proper setting up of the app.

At the main page of Sonarr, click Settings icon and you will be redirected to the first tab (Media management)

- Indexers

1) Click Indexers tab to set your custom indexer, where in this case you will be using a custom Jackett indexer.

2) Click the Custom button at Torznab section, under Torrent

At the new modal, choose a name of your choice (e.g. Jackett (Torrentz2)). Now for the rest two fields, you need to head back to your Jackett app.

Click the Copy Torznab Feed button in order to copy the link and paste it at the URL back at the Sonarr app.
Similarly, copy from the top right corner the API Key and paste it at the corresponding field back at the Sonarr app

At the Categories field, input the codes you have noted in the previous steps (or just click the wrench icon at the configured indexer back at your Jackett app) for your indexer to search in.
After inputting all fields, you can click the Test button to check if everything went smoothly and finally click the Save button:

You are now ready for adding your favourite shows via your custom indexer!