I did a showhn with similar idea(got a whooping 1 point and was flagged as spam which was later removed by mods), you paste your html and it encodes it into url, you can share the url without server involvement. I even added a url shortener because while technically feasible encoded url becomes long and QR code no longer works reliably. I also added annotation so you can add your comments and pass it to colleagues.

https://easyanalytica.com/tools/html-playground/

1. How does this work? window.open('about:blank'); and then a document write?

2. The share svg icons look very broken.