AuthenticatedMemberID()

Returns the member ID of the authenticated landing page user. Use this function only with Microsites when using Sender Authenticated Redirection. Not for use with CloudPages.

Marketing Cloud Engagement	✅ Yes
Marketing Cloud Next	❌ No

The AuthenticatedMemberID() function doesn’t accept any parameters.

You can call this function without passing any parameters.

The example outputs the member ID for the authenticated landing page user.