Debugging tracking with DebugView

Part 19 worked through trusting GA4 data for a real decision. That trust depends entirely on the tracking actually being correct in the first place — DebugView is the real tool for verifying that, in real time, before a broken implementation quietly corrupts weeks of reporting.

Enabling DebugView for a real testing session

Chrome extension: "Google Analytics Debugger" enabled, or
?_dbg=1 appended to the URL, or a real GTM Preview session active
  (part 4's installation method)

GA4 → Admin → DebugView

Any of these real methods flags the current browser session as a debug session — events from it appear in GA4's DebugView in genuine real time (seconds, not the standard reporting delay of up to 24-48 hours), letting a real, live test purchase be watched event by event as it happens.

Walking a real test purchase through DebugView

DebugView, live event stream during a real test checkout:
  page_view          ✓ fired, page_location correct
  view_item           ✓ fired, item_id: "BLC-002" correct
  add_to_cart         ✓ fired, matches item_id above
  begin_checkout       ✓ fired
  add_payment_info      ✗ did not fire — missing entirely
  purchase              ✓ fired, but items array is empty []

This single real debug session just caught two genuine, serious bugs at once: a missing step in part 9's full e-commerce sequence, and a purchase event firing with no product data attached — exactly the kind of gap that would otherwise surface only weeks later as an unexplained hole in the product-performance report from part 9, with no obvious cause visible from the reporting side alone.

Why this specific bug matters: it wouldn't show as an obvious error

Without DebugView: purchase events keep arriving, GA4's revenue
  totals look genuinely correct, but every product-level report
  (part 9) shows zero attributed revenue for every product, with
  no error message anywhere indicating why

This is exactly why DebugView matters beyond simply confirming events fire at all — a purchase event with an empty items array still counts toward total revenue correctly, so the bug is invisible in the top-line numbers and only surfaces as a silent, confusing gap in the product-level breakdown, easy to mistake for a real business problem rather than a tracking bug.

Inspecting real event parameters directly

DebugView → click the purchase event → parameter panel:
  transaction_id: "BLC-10391"
  value: 45.00
  currency: "USD"
  items: []          ← the real bug, visible directly here

DebugView's parameter panel is what makes the bug concretely diagnosable rather than just suspected — seeing the actual, real parameter values sent with each event, not just whether the event fired at all, is what reveals an empty items array as the specific, fixable root cause.

A real pre-launch checklist using DebugView

Before launching any new tracking (a new custom dimension from part
16, a new event for a new product line):
1. Enable a debug session
2. Trigger the real event manually
3. Confirm it appears in DebugView within seconds
4. Confirm every expected parameter is present and holds the real,
   correct value — not just that the event fired at all

This is the real, practical discipline that should run before trusting any new tracking implementation — confirming an event fires is necessary but insufficient; confirming its parameters actually hold correct, complete real data is what DebugView is specifically built to verify.

Real-time reports vs. DebugView: a genuine distinction

Realtime reports (part 5): show real, live traffic in aggregate — how
  many people are on the site right now, which pages
DebugView: shows one specific, flagged debug session's individual
  events and parameters in full detail

Part 5's Realtime report is for confirming tracking is live in general; DebugView is for confirming one specific implementation is correct in detail — genuinely different tools for genuinely different real questions.

Next: common Google Analytics mistakes — a direct, honest roundup of the real failure patterns this series has flagged individually, brought together in one place.