Lesson 1 of 7
The Debugging Mindset
The most expensive tracking mistakes are the silent ones: a tag that "looks fine" in the GTM UI but sends the wrong value, or nothing at all. The fix is a mindset: never trust a layer you haven't verified.
The three layers of truth
Tag fired?Tag Assistant→Request sent?DevTools Network→Data received?GA4 DebugView
A tag can fire (layer 1) but build a malformed request (layer 2), or send a perfect request that GA4 rejects (layer 3). Checking only the first is the classic trap. Good QA walks all three.
Key takeaway
"The tag fired" is the beginning, not the end. Confirm the request was sent and the destination received it before you call anything done.