GA4 vs Universal Analytics

Google officially retired Universal Analytics (UA), forcing every single web master to migrate to Google Analytics 4 (GA4).

The Fundamental Difference: Session vs Event

The core reason for this architectural shift lies in how data is conceptualized:

1. Universal Analytics (Hit-Based): Built around Sessions and Pageviews. Every action is tied to a user session that expires after 30 minutes of inactivity.
2. Google Analytics 4 (Event-Driven): Everything is an Event. A pageview is an event, a click is an event, even a session start is just an automatically collected event (session_start).

Code Example: Simulating a Custom GA4 Event Tracker

// A pure Javascript simulation of GA4 event model
function logGA4Event(eventName, params = {}) {
  const payload = {
    event: eventName,
    timestamp: Date.now(),
    client_id: localStorage.getItem('_ga_client_id'),
    properties: params
  };
  console.log("👉 Sending Event to GA4 Endpoint:", payload);
}

// Log a custom user fingerprint analysis action
logGA4Event('fingerprint_mismatch', {
  browser: 'Chrome',
  os: 'Windows',
  risk_score: 85
});