When the 3rd party cookies are blocked, the Visitor ID is not being shared between different domains. I have implemented a custom code to accomplish the Visitor.appendVisitorIDsTo(URL) solution: https://experienceleague.adobe.com/docs/id-service/using/id-service-api/methods/appendvisitorid.html?lang...

If the browser rejects 3rd party cookies and you are not implementing CNAMES(https://docs.adobe.com/help/en/id-service/using/reference/analytics-reference/cname.html) you will need to decorate every URL that redirects the user from DomainA to DomainB: https://docs.adobe.com/content/help/en/id-servic...

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