When you buy a book directly on D&D Beyond, Wizards of the Coast (via the platform) instantly attaches the license to your account. No key is involved. However, product keys exist for external distribution. These keys are generated by D&D Beyond and sold through authorized third-party retailers (like Amazon or local game stores) or distributed via promotional events.
In late 2023, Wizards of the Coast addressed the "product key" demand by introducing the . This is the closest contemporary answer to the "exclusive product key" query. product key dnd beyond exclusive