Verifying with DebugView and Realtime

After any tagging change, verify it live. GA4 gives you two tools.

Realtime (Reports > Realtime) shows activity from the last 30 minutes: users by page, event names, key events and user source. It is enough to confirm the tag loads and the big events fire, but it shows no parameters and mixes in everyone else's traffic.

DebugView (Admin > DebugView) shows a single browser's event stream, second by second, with every parameter and user property, including whether an event was marked as a key event. A browser appears there only when its events carry the debug_mode parameter. Three ways to enable it:

• gtag('config', 'G-...', { debug_mode: true }) on a staging build,
• the Google Analytics Debugger Chrome extension, which sets it for every site,
• Tag Assistant preview mode (tagassistant.google.com), which is the GTM debugger and also marks hits as debug.

Tag Assistant adds a second view: for each tag it shows which trigger fired, the variables resolved and the exact request sent, so it is the best tool when the question is "why did this tag not fire". Your browser's Network tab, filtered to collect?, shows the raw request with every parameter as query string fields and is the final word.

A verification routine: load the page (expect page_view, session_start, first_visit on a fresh profile); perform the action (expect your event with the right parameters and numeric types); check there are no duplicates; confirm the key event flag. Then wait 24 to 48 hours and check the Events report shows it.