This site is 100% clientside - meaning it all runs in your browser and does not have a server or backend of its own. For this reason, all of the deck data is stored inside the URL 'code' that is generated, and nowhere else.

The code parses your decklist and then queries the Scryfall API to fetch card images and other information. Next, it does a little bit of ordering by card type and CMC cost, etc, before displaying the cards to you.

The entire source code is available on GitHub if you are interested. If you find any bugs, please report them on GitHub as well. Thanks.