Universal Analytics is gone, and GA4 is not a reskin — it’s a different data model. If you treat the migration like a settings change, you’ll lose history and trust in your numbers. Treat it like a small project instead.
Run the two in parallel first
Create the GA4 property early and let it collect alongside Universal Analytics for as long as you can. You want a few months of overlap so you can sanity-check GA4’s numbers against a source you already trust before you rely on it. Set up the property, add the data stream, and install the tag through Google Tag Manager rather than hard-coding it — you’ll be changing things often.
Rethink events, don’t port them
In GA4 everything is an event, and the old category / action / label model doesn’t carry over. Start from the questions you actually answer with analytics, then design the handful of events that answer them. Use GA4’s automatically collected and enhanced-measurement events where they fit, and reserve custom events for the things specific to your product. Fewer, well-named events beat a faithful copy of your old setup.
Rebuild conversions as key events
Goals are now “key events” you mark from your event list. Re-create only the ones that map to real business outcomes, and confirm they fire with the DebugView before you trust them. This is also the moment to wire GA4 to Google Ads cleanly, because the conversion plumbing is different.
The gotchas nobody warns you about
Data is not backfilled, so the day you create the property is the day your history starts — which is why the parallel run matters. Reporting is sampled and thresholded differently, so numbers won’t match Universal Analytics one-to-one; explain that to stakeholders up front. And the default data retention is short — bump it in settings on day one, or you’ll wonder where last quarter went.
Get the property created early, keep the event list small and intentional, and verify everything in DebugView. The migration is dull, but a clean GA4 setup pays for itself every time someone asks “where did this number come from?”