Google Analytics 4 Event Builder

In GA4, everything is an event — pageviews, button clicks, purchases, scrolls. Unlike Universal Analytics which used categories/actions/labels, GA4 uses a flexible key-value parameter model. Each event has a name and up to 25 custom parameters. This makes GA4 much more flexible but requires more intentional event design.

gtag() is the direct Google Analytics SDK method — call it directly on pages where you load the GA4 tag. dataLayer.push() is for Google Tag Manager (GTM) — you push events to the dataLayer and GTM picks them up and forwards to GA4. Use dataLayer if you manage tracking via GTM; use gtag() for direct GA4 implementation.

GA4 has a set of recommended events with predefined schemas — like purchase, add_to_cart, begin_checkout, sign_up, login, search, view_item, generate_lead. Using these enables automatic integration with Google Ads, BigQuery exports, and built-in GA4 reports. Always prefer recommended events over custom events when the semantic fits.

Each event can have up to 25 custom parameters. GA4 automatically collects some parameters (page_location, page_title, session_id, etc.). Custom parameters must be registered as 'custom dimensions' or 'custom metrics' in the GA4 property settings before they appear in reports. String values max 100 chars, numeric values as numbers.

Use Google Analytics Debugview (in GA4 admin → DebugView), the GA4 Tag Assistant Chrome extension, or send events in debug mode by adding &_dbg=1 to your gtag.js URL. Also check the Network tab in DevTools for requests to google-analytics.com/g/collect to verify event payloads are being sent.

The currency parameter uses ISO 4217 currency codes (USD, EUR, GBP, JPY, etc.). The value parameter should be a numeric amount — do not include currency symbols. For example: gtag('event', 'purchase', { currency: 'USD', value: 29.99, transaction_id: 'T_12345' }). This is required for revenue tracking in GA4.