I thought that it was possible to make the embedded game only playable if you have purchsed it, but when I checked the page it is playable without purchasing, so I've temporarily disabled it.  I'm hoping that the only way to do this isn't to make people download the HTML file, because 1) it is less convenient and defeats the purpose of making it playable in the browser, and 2) trying to open an HTML game from a file doesn't work because it detects a security problem and refuses to play.

How do I make the embedded game only playable to those who have purchased it?

As far as I understand it is not possible in Itch.

You can only place payment restrictions on the download, but not on the online execution.

What you could do, but it is something that you must program on your own, is through the itch API, check if the person who is playing has actually paid for your game. But I don't know how easy it is to implement.

I see.  Thank you.