Map a custom subdomain to server-side GTM on Google Cloud with a Load Balancer

Chapters

1. 0:00Requirements
2. 0:45Create an IP address
3. 2:42Update the DNS manager
4. 3:46Create the SSL certificate
5. 5:34Start the Load Balancer settings
6. 7:04Set up the front end
7. 8:27Set up the back end
8. 11:39Set up routing rules
9. 12:35Review and finalize
10. 13:13Test the custom domain

What you need before you start

• A server-side GTM container already running on Google Cloud
• Project Owner or Editor in Google Cloud (or Compute Network Admin, Compute Instance Admin and Security Admin)
• Access to your DNS manager
• Editor, Publisher or Owner access in Google Tag Manager
• The Compute Engine and Certificate Manager APIs turned on

Steps covered in the video

1. Reserve a global static IPv4 address on the Premium network tier.
2. Add an A record for your subdomain that points to that IP. Avoid obvious names like 'tracking', which some ad blockers look for.
3. Create a Google-managed SSL certificate for the subdomain.
4. Create a global external Application Load Balancer.
5. Front end: HTTPS on port 443 with your IP and certificate, plus the HTTP to HTTPS redirect.
6. Back end: a serverless network endpoint group pointing to your Cloud Run GTM service.
7. Routing rule: your subdomain, path /*, to that back end.
8. Add the subdomain in the server container settings and check /healthy and Tag Assistant.

Common questions

Resources

• Full written guide

Recorded in September 2025. Some screens may look different today.

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