Multi-Domain / Multi-Brand Setup

<script
  src="https://edge.b2metric.com/b2m-web-sdk.js"
  data-api-key="YOUR_API_KEY"
  data-cookie-domain="auto"
  data-app-identifier="yourbrand.com"></script>

cookieDomain="auto" (the default) shares UTM/campaign/referrer data and device identity across your subdomains as visitors move between them.

What is and isn't shared across subdomains

Session state and login identity are never shared across subdomains, by design — so a sibling subdomain running a different app can't see who's logged in elsewhere on your domain. app-identifier is used to break down reporting by domain and isn't needed on a single-domain setup.