YouTube Engagement

The native GTM YouTube Video trigger initially failed to fire at all — root cause was two-fold: the embedded iframe was missing enablejsapi=1&origin= params, and separately, script-src was missing a CSP allowlist entry for youtube.com.

After fixing both, native detection worked — but so did a custom-built, explicit dataLayer-based tracking solution built in parallel, resulting in duplicate event firing for the same video watch.

Diagnosis technique worth keeping regardless of this specific bug’s outcome: when suspecting two independent tracking systems are firing for the same event, check the fired event’s own field list for values one system’s code doesn’t reference at all. Here, videoDuration/videoCurrentTime/videoElapsedTime/videoVisible appeared in a fired event despite the custom code never setting any of those fields — direct proof GTM’s native auto-detection was firing independently and simultaneously.

Final state: reverted to native-trigger-only. The live GTM export confirms only one native YouTube Video trigger and one clean GA4 - YouTube Engagement tag currently exist — no duplicate custom tag remains. But final single-firing verification after the revert was not conclusively confirmed before this was deprioritized.

The tag’s event name is computed dynamically via a JS - Video Event Name variable ("video_" + the native Video Status built-in variable) — this is a thin formatting layer over the native trigger’s own data, not a second parallel tracking system.