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5 mistakes that kill server-side migrations
Jeff Sauer
February 19, 2026
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Everything looks perfect in GTM preview mode…
Tags firing. Requests flowing. Debug view showing events in GA4.
You publish.
You celebrate.
Then a week later, you check the data and half of it is missing.
Or worse—your conversion tracking is completely dead.
Here's the truth: Server-side tracking has a massive failure rate because there are five specific walls that almost everyone hits, and the tutorials completely skip over them.
Let me give you three of the big ones:
Mistake #1: The Missing Server URL
Your web GTM preview says everything's working. But your server container? Completely empty.
Here's what's happening: The Google tag defaults to sending data directly to Google, not through your server. One missing parameter. One typo. Hours of staring at an empty screen.
Mistake #2: The Tag Sequencing Failure
Your data is flowing. GA4 is receiving events.
Then you open your acquisition reports and see a massive spike in "not set" traffic.
Your events are arriving without session context. Attribution is broken.
Why? Your event tags are firing before your configuration tag loads. Those events become orphans.
Mistake #3: The Preview Mode Trap
This one is brutal.
Preview mode shows perfect data. You publish. You move on.
A week later, your client asks why conversion volume dropped 60%.
Preview mode bypasses ad blockers. It bypasses privacy extensions. You tested in a perfect environment. You deployed to a hostile one.
And those are just three of the five walls.
The other two? They're even more subtle. And they'll kill your implementation just as fast.
In the video, I walk through all five mistakes, the exact symptoms to watch for, and how to fix each one before you go live.
I also put together a pre-flight checklist—the exact list of things to verify before you publish so you don't spend hours debugging in production.
Comment "FLIGHT" on the video and I'll send it to you.
Server-side tracking isn't hard once you know where the walls are.
Most people just never get told where to look.
To Your Measured Success!
--Jeff Sauer
CEO of MeasureU
P.S. If you haven't grabbed your seat for the Server-Side Tracking in 90 Minutes workshop yet, today's the day. We go live in 4 hours at 1PM Eastern—and this is the only time we're running this format this quarter. Miss it, and you're back to piecing together YouTube tutorials alone. Reserve your spot here before we start.
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