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overwriteCrossDomainMCIDAndAID

This property overwrites a visitor's Experience Cloud and Analytics IDs as they navigate from one domain to a second domain. To overwrite an ID, you must own and have implemented the ID service on each domain. This code does not let you overwrite IDs on domains you do not control.
Syntax:
Visitor.overwriteCrossDomainMCIDAndAID: true|false
(default is
false
)
Code Sample
Your JavaScript code could look similar to the following example.
//Call the ID service var visitor = Visitor.getInstance("INSERT-MARKETING-CLOUD-ID-HERE", { ... //Set overwrite property overwriteCrossDomainMCIDAndAID: true });
Use Cases
To track site visitors, the ID service writes a Experience Cloud ID (or MID) to a browser cookie. The following table lists and describes the common use cases where you might want to overwrite an existing MID set by the ID service in another domain.
Use Case
Description
Identify visitors on different domain landing pages
Let's say you own Domains A and B. In this case you can set
Visitor.overwriteCrossDomainMCIDAndAID: true
when:
  • Each domain has a it's own landing page.
  • A visitor already has a cookie (and a MID) set from a previous visit to Domain B.
  • You want to consistently identify a visitor if they come to Domain B from Domain A.
Identify visitors across landing and conversion pages
Let's say you own Domains A and B. In this case, you can set
Visitor.overwriteCrossDomainMCIDAndAID: true
when:
  • Domain A is a landing page.
  • Domain B is a separate conversion, booking, or other end-of-workflow page.
  • A visitor already has a cookie (and a MID) set from a previous visit to Domain B and you know these are less desirable client-side MIDs rather than server-side MIDs.
  • You want to consistently identify a visitor if they come to Domain B from Domain A.
Identify visitors from mobile apps to web browsers
This use case is slightly different. It involves identifying users as they move from a mobile app to your website. In this case, your visitor already has a MID set locally by a mobile app and they have a different MID set in a cookie on your website. You can set
Visitor.overwriteCrossDomainMCIDAndAID: true
to overwrite the MID set in the browser cookie with the MID set by the mobile app.