appendVisitorIDsTo (Cross-Domain Tracking) appendvisitoridsto-cross-domain-tracking

Last update: May 22, 2026

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Cross Domain tracking will not work as intended if the ECID is rejected initially (or previously). It will not check the existing IDs that were either passed via URL or previously existed in the cookie, considering those were the IDs when the consent was set to “NO”.

This function lets you share a visitor’s ECID across domains when browsers block third-party cookies. To use this function, you must have implemented the Visitor ID Service and own the source and destination domains. Available in VisitorAPI.js version 1.7.0 or higher.

Contents:

Track Visitors Across Domains When Browsers Block Third-Party Cookies section-7251d88befd440b4b79520e33c5aa44a

Visitor ID Service writes a first- and third-party cookie to the browser when a person visit your site (see Cookies and the Visitor ID Service ). The first-party cookie contains the MID, a unique ID for that visitor. The third-party cookie contains another ID used by the Visitor ID Service to generate the MID. When a browser blocks this third-party cookie, the Visitor ID Service cannot:

Regenerate the unique ID for that site visitor when they navigate to another domain.
Track visitors across different domains owned by your organization.

To help solve this problem, implement Visitor.appendVisitorIDsTo( *url*). This property lets the Visitor ID Service track site visitors across multiple domains even when their browsers block third-party cookies. It works like this:

As a visitor browses to your other domains, the Visitor.appendVisitorIDsTo( *url*) appends the MID as a query parameter in the URL redirect from the original domain to the destination domain.
The Visitor ID Service code on the destination domain extracts the MID from the URL instead of sending a request to Adobe for that visitor’s ID. This request includes the third-party cookie ID, which is not available in this case.
The Visitor ID Service code on the destination page uses the passed-in MID to track the visitor.

See the code sample for details.

Append Visitor ID Code Sample section-62d55f7f986542b0b9238e483d50d7b0

The following example code can help you get started with the appendVisitorIDsTo function:

TIP

This code can be placed in the Custom Code editor that’s part of the Adobe Analytics extension or at the top of AppMeasurement.js.

var adbeDomains = ["marketo.com", "figma.com", "workfront.com"];
var visitor = Visitor.getInstance("9E1005A551ED61CA0A490D45@AdobeOrg", {
  trackingServer: "sstats.adobe.com",
  trackingServerSecure: "sstats.adobe.com",
  marketingCloudServer: "sstats.adobe.com",
  marketingCloudServerSecure: "sstats.adobe.com"
});
adbeDomains.forEach(function(domain) {
  var domainRegex = RegExp(domain);
  if (!domainRegex.test(location.hostname)) {
    hrefSelector = '[href*="' + domain + '"]';
    document.querySelectorAll(hrefSelector).forEach(function(href) {
      href.addEventListener('mousedown', function(event) {
        var destinationURLWithVisitorIDs = visitor.appendVisitorIDsTo(event.currentTarget.href)
        event.currentTarget.href = destinationURLWithVisitorIDs.replace(/MCAID%3D.*%7CMCORGID/, 'MCAID%3D%7CMCORGID');
      });
    });
  }
});

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