sGTM Test Lab
Updated August 2026 · 4 min read
Two independent tools for testing a live server-side container: route real traffic into Google Tag Manager Preview, and stop reviewed advertising destinations receiving your test events.
What sGTM Test Lab is
Testing a server-side container against real traffic has always involved a trade-off. Preview mode shows you what is happening, but only for your own session. And once a tag fires, it fires — a test purchase reaches your advertising platforms as a genuine conversion.
sGTM Test Lab is a Power-Up with two independent tools that address those separately:
- sGTM Live Debug routes selected live requests into Google Tag Manager Preview, so you can see real traffic in the debug pane.
- Ad-Safe Test Mode stops reviewed advertising destinations receiving deliveries on positively-identified Preview requests, so testing does not create real conversions.
They are separate leases. You can run either alone, or both together.
Choose between Live Debug and Ad-Safe Test Mode
| You want to… | Use | |---|---| | See what a real visitor's request does inside your container | sGTM Live Debug | | Confirm an event reaches the container at all | View incoming container requests | | Run a test purchase without it landing in an ad platform as a conversion | Ad-Safe Test Mode | | Watch a real conversion path end-to-end without polluting reporting | Both, together |
How the tools work independently
Each tool holds its own lease with its own status and its own expiry. Enabling one does not enable the other, and stopping one does not stop the other. The only shared control is End Test Session, which stops both.
Both tools need a Google Tag Manager Preview credential. If Live Debug is already running when you turn on Ad-Safe Test Mode, the credential is reused:
The active sGTM Live Debug credential will be reused securely. You do not need to paste it again.
If you enable Ad-Safe Test Mode on its own, you supply the credential yourself.
Preview credential handling
You paste the value of the X-Gtm-Server-Preview header from Google Tag Manager. The panel is
explicit about what happens to it:
Shown while you review it. After activation it is encrypted at rest, never returned by TagVolt, and removed when this one-hour session ends.
When Ad-Safe Test Mode takes its own credential, only a one-way fingerprint is retained — the plaintext token is never stored. The credential exists to bind genuine Preview traffic to your session, so that neither tool can act on ordinary visitors.
One-hour sessions
Both leases last exactly one hour. This is not a soft limit or an idle timeout — it is a fixed duration from the moment the session starts.
An expired session does not clean itself up. When the hour elapses while a tool is still on, its status becomes needs attention rather than switching itself off. You cannot start a new session until the expired one is ended — attempting it reports that the expired session's cleanup is still pending. Use End Test Session to clear it.
The one-hour bound is deliberate. Both tools change how a live container behaves, and a session that could be left running indefinitely by accident is a much larger risk than one that has to be renewed.
Permissions
Test Lab is limited to workspace owners and administrators. Members with other roles can see the container but cannot start, stop or configure either tool.
Fail-open behaviour
Both tools are built to fail towards delivery rather than towards loss. If a request cannot be positively identified as Preview traffic, it is treated as ordinary traffic and handled normally.
The consequence is worth stating plainly: an occasional test event may be delivered for real rather than being held back. That is the deliberate trade — the alternative, failing towards blocking, would risk dropping genuine customer conversions, which is the more expensive mistake.
End Test Session
The shared control at the bottom of the panel:
Stop sGTM Live Debug and Ad-Safe Mode together.
End Test Session clears both leases and the session's stored state, including the credential. Use it whenever you have finished, and always when a session has expired into a needs-attention state.
FAQ
Do I have to use both tools?
No. They are independent. Live Debug alone is useful for inspecting behaviour; Ad-Safe Test Mode alone is useful when you already know what you want to test and only need it not to count.
Does Ad-Safe Test Mode require request logging?
No. It operates without Outgoing request logging, and in that mode it stores no request evidence.
What happens to ordinary visitors while a session is running?
Nothing. Both tools act only on requests positively identified as belonging to your Preview session. Ordinary traffic is routed and delivered exactly as usual.
Can I extend a session past an hour?
No. End the session and start a new one.
Why is my session showing "needs attention"?
The hour elapsed while the tool was still on. Press End Test Session to clear it, then start again if you still need it.