Why debugging matters

A measurement plan is only as good as its implementation. Debugging is how you confirm that:
events fire at the right time, parameters are correct, and data actually reaches GA4.
Without debugging, you might report on broken or incomplete data without realizing it.

Method 1: GTM Preview Mode (Tag Assistant)

GTM Preview is the most useful method when you manage tracking through Google Tag Manager.
It shows which tags fired, which didn’t, and exactly why.

• See the exact trigger conditions
• Inspect variables (Click URL, Page Path, Data Layer values)
• Confirm tag firing order

Method 2: OmniBug

OmniBug is a browser extension that shows the analytics requests being sent from your site.
Think of it as “proof” that data left the browser.

• Validate event names and parameters
• Confirm correct GA4 Measurement ID
• Spot duplicates (same event sent twice)

Method 3: GA4 DebugView (debug_mode=true)

GA4 DebugView lets you see events in near real-time as they arrive in GA4—only for sessions marked as debug sessions.
GTM Preview automatically enables debug_mode, and you can also enable it via URL parameters in certain cases.

Which method should you use?

Extra mention: Network Tab (advanced)

The browser Network tab is the most technical but most accurate approach. It shows raw requests being sent.
We mention it as an advanced option, but we’ll keep our main focus on GTM Preview, OmniBug, and GA4 DebugView.