Multi Domains — Sharing an sGTM container across domains

What is Multi Domains?

The Multi Domains add-on lets you share one server-side GTM container across multiple domains or subdomains. All domains send data to the same sGTM endpoint, which simplifies management and reduces costs.

Why use Multi Domains?

• Multi-site e-commerce: One sGTM for all stores (cz, sk, de, etc.).
• White-label SaaS: One sGTM for all customer subdomains.
• Staging + Production: www.site.cz + staging.site.cz share an sGTM.
• Cost savings: 1 sGTM container instead of 5 = 80% savings.

How to activate

1. Go to Dashboard → Add-ons
2. Turn on the "Multi Domains" toggle
3. The power-up automatically enables cross-domain tracking
4. Add all domains to Dashboard → Domains

Domain configuration

In Dashboard → Domains add all the domains that will use the same sGTM container:

Primary: track.site.cz → sGTM container GTM-XXXXXX
Additional:
  - www.site.cz → uses track.site.cz
  - www.site.sk → uses track.site.cz
  - staging.site.cz → uses track.site.cz

DNS configuration

All domains must have a CNAME record pointing to the primary tracking domain:

track.site.cz.     CNAME   sgtm.datanostro.com.
www.site.cz.       CNAME   track.site.cz.
www.site.sk.       CNAME   track.site.cz.
staging.site.cz.   CNAME   track.site.cz.

GTM Snippet on all domains

Each domain uses the same GTM snippet with a server_container_url pointing to the primary tracking domain:

<script>
(function(w,d,s,l,i){
  w[l]=w[l]||[];
  w[l].push({'gtm.start': new Date().getTime(),event:'gtm.js'});
  var f=d.getElementsByTagName(s)[0],
      j=d.createElement(s),
      dl=l!='dataLayer'?'&l='+l:'';
  j.async=true;
  j.src='https://track.site.cz/gtm.js?id='+i+dl;
  f.parentNode.insertBefore(j,f);
})(window,document,'script','dataLayer','GTM-XXXXXX');
</script>

Cookie sharing

For cross-domain cookie sharing set the cookie domain to the root domain:

// GTM server-side — Cookie Settings
cookie_domain: .site.cz  // Shared across www.site.cz, staging.site.cz, etc.
cookie_domain: .site.sk  // Shared for the SK domain

Benefits of Multi Domains

• Centralized management: One GTM container for all domains.
• Unified reporting: All data in one GA4 property.
• Lower latency: One sGTM endpoint = fewer DNS lookups.
• Cost-efficient: 1 sGTM container = 1 plan instead of N plans.

Limitations

• Max 10 domains per sGTM container (PRO+ plan)
• All domains must have the same owner (SSL certificate)
• Cross-domain cookies require third-party cookie consent (GDPR)