Jackett is a program available for OSX, Windows, and Linux that works as a proxy server to translate queries from apps (Sonarr, Radarr, Lidarr, SickRage, CouchPotato, etc.) into tracker-site-specific HTTP queries, parses the HTML response, and 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.
Setting up Jackett is really simple. First download the copy that you would like to use and install it as you would any normal program. We use the Docker version on our Linux server and you can read about how to install that here.
Once Jackett is running it will stay open in the background and can be opened using your favorite internet browser and navigating to http://localhost:9117.
To add an indexer, click the button and choose an indexer from the list. If you choose a private indexer, you will need to click the icon to the right and login.
You can now click and paste it into the URL section when adding a custom Torznab indexer via Sonarr, Radarr, etc. The API Key from Jackett will also need pasted into the custom Torznab settings so that Jackett and the external program can communicate.