Server side GTM with multiple domains

In this guide

How it works Set up with Open Tracked Separate sites inside the container Cookies, consent and data When to use separate containers Cost Common problems Frequently asked questions

Key takeaways

Each site needs its own tagging subdomain. They can all point to one container.
Separate sites inside the container with hostname variables and triggers.
Keep different clients in different containers, always.

Agencies and multi-brand businesses often ask whether they can use one server container for many sites. They can, within limits, and the saving is real: one container to maintain and one plan to pay for. The risks are mixing data between sites and a harder-to-read container. This page explains how to set it up cleanly and when to choose separate containers. It follows multi-domain tracking and server-side tracking for agencies.

How it works

Each website has its own web container (or a shared one with conditions) and sends events to its own tagging subdomain, such as data.brand-a.com and data.brand-b.com. Both subdomains point to the same server container. The server sees the hostname of each request. You use it to decide what happens.

Live view

Watch events arrive, live

A sample feed. In Open Tracked you see the same stream for your own store.

Set up with Open Tracked

Choose a plan with Multi-Domains

The Multi-Domains power-up is on the Business plan and above.

Turn it on

In the container's power-ups.

Add each tagging subdomain

In Settings, Domains.

Point each DNS record and verify

Wait until each shows Verified.

Set the server container URL in each site's web container

To its own tagging subdomain.

Separate sites inside the container

Create a request hostname variable (the Host header).
Add a lookup table variable that maps each hostname to its GA4 measurement ID, Meta dataset ID and token.
Use the lookup variables in your tags, so one set of tags serves all sites.
Add hostname conditions to triggers where a site has tags the others do not.

Hostname	GA4 ID	Meta dataset
data.brand-a.com	G-AAAA	Dataset A
data.brand-b.com	G-BBBB	Dataset B

Trusted

Brands that grow on cleaner data

Stores and agencies use Open Tracked to see which ads earn the sale.

Cookies are set per tagging subdomain, so each site's visitors get cookies on that site.
Consent is recorded per site. Make sure the server container receives the right consent state for each.
Do not merge customer data between brands unless you have a lawful basis and say so in your notice.

When to use separate containers

Choose One container if

sites of the same company with the same tags
one team manages them
the sites share the same ad accounts or you can map IDs cleanly

Choose Separate containers if

different clients or legal entities
different teams that need separate access
very different tag sets
you want simple exports per site

Cost

One container on one plan serves all the domains, as long as the total requests fit the plan. Open Tracked plans are sized from 15,000 to 20 million requests a month. Add up the requests of all sites before you choose. See how much a server GTM costs.

Common problems

SymptomEvents from one site go to another site's property

Likely causeThe tag has a fixed ID.

FixUse the lookup variable.

SymptomA tag fires on the wrong site

Likely causeNo hostname condition.

FixAdd one.

SymptomConsent from one site applies to another

Likely causeA shared consent variable.

FixRead consent per request.

SymptomRequests exceed the plan

Likely causeAll sites together are larger than expected.

FixReview the plan.

0 of 6 done

Each site has its own tagging subdomainA lookup table maps hostnames to IDsTriggers have hostname conditions where neededConsent is per siteClients are in separate containersTotal requests fit the plan

Set up in minutes

Connected in minutes

Add your domain, install the pixel, connect your ad platforms and watch the first events land.

Frequently asked questions

Can one server container serve several websites?

Yes, if each site has its own tagging subdomain pointing to it and you separate sites by hostname.

Which Open Tracked plan includes Multi-Domains?

Business and above.

How do I send each site to its own GA4 property?

Use a lookup table variable that maps the hostname to a measurement ID.

Should different clients share a container?

No. Use separate containers for different clients.

Does it change my cost?

You pay for one plan sized to the total requests.

Do I need spreadsheets to read my results?

No. Once tracking is live, the Open Tracked analytics shows spend, revenue, ROAS and profit, and you can ask Ari, the built-in AI assistant, questions about your own numbers in plain words. Ari's allowance depends on your analytics plan.

Is Open Tracked different from Open Track or Open Space Track?

No. Open Tracked is the official name of our server-side tracking platform, and the website is opentracked.io. Many people search for it as Open Track, OpenTrack or Open Space Track. All of them lead to the same product: server-side Google Tag Manager hosting, first-party analytics and a CRM pipeline.

Fix your tracking at the source

Open Tracked hosts your server-side Tag Manager, keeps first-party cookies alive and shows what each ad is really worth.

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Written by

The Open Tracked team

We build Open Tracked: server-side tracking hosting, analytics and the tools around them, for stores that spend on ads. Questions about this guide, or an idea for the next one?

Write to us Read the docs

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