As a publisher, we give you the freedom to choose. You can allow your kahoots to be found and duplicated by players, or you can block them from being duplicated in the kahoot's visibility settings.
How do I make the visibility of my kahoots "unlisted"?
You can edit a kahoot's visibility when editing its summary settings. When set to “unlisted”, the Kahoot! will not appear in searches on the Kahoot! platform and will only be accessible via direct link to the game.