A Practical Server-Side GTM Checklist
Moving to server-side GTM is not a migration, it's a redesign.
Server-side GTM is one of the most powerful infrastructure changes a marketing team can make. It is also one of the easiest to mess up. We have seen migrations that recover 20% of lost signal, and migrations that create data silos that take months to unwind.
The difference is usually planning. Treat server-side GTM as a redesign, not a migration. You are not just moving tags from one container to another. You are changing where data is collected, who owns it, and how it flows into your tools.
Start with your event taxonomy. If your client-side tagging is already messy, server-side will make the mess more opaque. Document every event, parameter, and destination before touching the container.
Next, design your data flow. Which events go to which destinations? Which parameters need enrichment from a CRM or lookup table? Where do you need consent checks before sending data? Draw it out before you build it.
Then think about hosting and cost. App Engine vs. Cloud Run, regional deployment, logging, and debugging access all matter. The cheapest default setup is rarely the right one for a production marketing stack.
Finally, test obsessively. Use preview mode, debug endpoints, and real conversion events. Compare client-side and server-side outputs side by side for at least two weeks before you switch anything over completely. The last 10% of edge cases will cause 90% of your headaches.