How does the Marketing Cloud ID Service (MCID) maintain a consistent ID across domains and web properties in browsers that accept third-party cookies?
It does this by utilizing the IMS org ID deployed in your VisitorAPI.js file and a third-party Demdex cookie.
The following knowledge base article shows how this process works and the associated network requests. There is also a video that walks through a scenario.
Thanks for The information Mr Jantzen belliston , That was really helpful.
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