GA4 migration: what most teams get wrong

Two years in, and GA4 migrations are still producing bad data. Here are the five setup mistakes we see on almost every audit.

GA4 has been mandatory for two years now. Most teams have completed the migration. And most of those migrations are quietly producing data that nobody should trust.

We audit GA4 setups regularly. The same mistakes show up every time. Here are the five we see most often.

1. Skipping the Universal Analytics event audit

Before you migrate, you need to know exactly what UA was tracking. Custom events, goals, enhanced e-commerce. If you don't document what you had, you can't replicate it in GA4, and you won't notice what's missing until someone asks for data you no longer have.

2. Wrong data retention settings

GA4 defaults to two months of event data retention. Most teams never change this. If you want year-over-year comparisons, you need to set it to 14 months immediately. You can't backfill data you didn't retain.

3. Not filtering internal traffic

Your team is browsing the site. Their sessions are in your data. In many SMBs, internal traffic can account for 10-20% of total sessions. Set up an internal traffic filter using IP ranges or developer traffic definitions and exclude it from all reporting views.

4. Missing conversion events

GA4 doesn't auto-detect conversions. You have to mark events as conversions explicitly. Form submissions, calls, purchases, sign-ups, whatever matters to your business needs to be flagged. Many GA4 setups we audit have zero configured conversion events.

5. Ignoring custom dimensions from day one

Custom dimensions let you pass business-specific data into GA4: customer type, plan tier, logged-in status, whatever's relevant. They're easy to skip at setup because they feel optional. They're not. Once you need them, you can't backfill the historical data.

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