GA4 vs Universal Analytics: What Changed and Why It Matters

Universal Analytics stopped processing data in July 2024. If you migrated to GA4 but never validated your setup, your data is likely incomplete. Here is what actually changed and what you need to know.

The Core Difference: Sessions vs Events

Universal Analytics was built on a session/pageview model. Every interaction was tied to a session. GA4 is event-based. Everything — page views, clicks, scrolls, purchases — is an event.

This is not just a philosophical difference. It changes how data is collected, stored, and reported.

What You Lost in the Migration

1. Views Are Gone

UA had Account > Property > View. Views let you create filtered perspectives (e.g., exclude internal traffic, filter by country). GA4 has no views. You get one data stream and use report filters or Explorations to segment.

2. Custom Reports Were Not Migrated

Any custom report or dashboard you built in UA does not exist in GA4. You need to rebuild them using Explorations or Looker Studio.

3. Historical Data Is Gone

UA data was not transferred to GA4. If you need historical comparisons, you should have exported UA data to BigQuery before the deadline. If you did not, that data is gone.

4. Content Grouping Works Differently

In UA, you could set content groups via the tracking code, GTM, or admin rules. In GA4, content grouping is done through a content_group parameter on the page_view event:

gtag('event', 'page_view', {
  content_group: 'Product Pages'
});
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What You Gained

1. Cross-Platform Tracking

GA4 natively tracks web and app in one property. If you have both, a single user journey can span your website and mobile app.

2. Better User Identity

GA4 uses three identity methods: User-ID (your login system), Google Signals (logged-in Google users), and Device ID (cookie). This gives better cross-device attribution.

3. Predictive Metrics

GA4 offers machine learning predictions: purchase probability, churn probability, and predicted revenue. These require sufficient data volume to activate.

4. BigQuery Export (No 360 Required)

In UA, BigQuery export was only available in the paid 360 version. GA4 gives every property BigQuery export at no cost.

5. Enhanced Measurement

GA4 automatically tracks scrolls, outbound clicks, site search, video engagement, and file downloads without any GTM configuration. In UA, these all required custom setup.

Common Migration Mistakes

1. Not configuring key events. UA goals did not auto-migrate. You need to manually mark events as key events in GA4 Admin > Key events.

2. Duplicate tracking. Many sites have both the gtag.js snippet AND GTM firing GA4. This causes double-counted sessions and events.

3. Missing enhanced ecommerce. UA ecommerce events do not translate to GA4 ecommerce events. The event names and parameter structures are completely different (purchase vs ecommerce:purchase).

4. Ignoring data retention. GA4 defaults to 2 months of data retention. Change this to 14 months in Admin > Data Settings > Data Retention.

5. Not linking Google Ads. The link does not carry over from UA. Reconnect in Admin > Product links > Google Ads.

What to Validate Now

If you migrated but never audited, check these immediately:

1. Are key events (conversions) configured and firing?
2. Is enhanced measurement enabled for scrolls, outbound clicks, and file downloads?
3. Is data retention set to 14 months?
4. Are Google Ads and Search Console linked?
5. Is cross-domain tracking configured if you have multiple domains?
6. Are custom dimensions and metrics recreated?

Run a GA4 audit on your property — start your audit →