What a pile of trash, and I had to pay $10 to find out because the Free version is vaporware and only gives you a silly checkout editor simulation. Actual checkout is broken. Often messages boxes are hidden under other elements. It seems to block checkout by removing shipping methods, however, Checkout Extensibility keeps trying to add them back in, so you just see shipping rates calculated over and over and blinking. Finally, it is trivial to defeat since it's just running JavaScript in the browser. This won't stop bots or resellers or anyone else who knows how trivial it is to defeat. Finally, finally, it's EXTREMELY expensive considering our order volume. We should be refunded our money. Don't waste $10 and your time to find out it doesn't work. One more thing: it breaks the customer address book. Blocking the app's JavaScript or uninstalling fixes checkout. And, yes, the developer should use Shopify Functions NOT JavaScript. Completely over-hyped, over-priced app that breaks checkout and doesn't do what it's purported to do.