Google Analytics 4 (GA4) Explained: Measurement IDs & Events

Google Analytics 4 (GA4) is Google’s current analytics platform, it replaced Universal Analytics in 2023. It measures pageviews, events, conversions and audiences across web and app, and is almost always the foundation of a site’s measurement stack.

What the G-XXXX ID means

Every GA4 property has a Measurement ID in the form G-XXXXXXXXXX. That ID tells the browser which GA4 property to send data to. In Tag Explorer you’ll see it as the tag’s number.

Configuration vs Event tags

In Google Tag Manager you’ll often see two GA4 tag types:

• GA4 Configuration (or the newer Google Tag), loads GA4 and sends the initial page_view. There should normally be one per property.
• GA4 Event, sends specific interactions (clicks, form submits, purchases). A site can have many.

Why it matters

GA4 is how you understand traffic sources, on-site behaviour and conversion paths. A missing or duplicated GA4 tag means inaccurate sessions and conversions, which then misleads every decision built on that data.

How to check yours is working

Run your site through our free Tag Explorer tool, it shows every tag on the page, nested under its GTM container, with the tracking IDs. To confirm a tag actually fires, use GTM’s Preview mode or your browser’s DevTools Network tab.

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Part of the Shipwreck Studio Tag Guide. Scan any page with Tag Explorer to see its full tag tree and spot duplicates.