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.
Sam Daniel
Founder, Aanya Ari Consulting · April 2026
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.
If you're not sure whether your GA4 setup is producing reliable data, a structured audit will tell you quickly. Most teams are surprised by what they find.
Frequently asked
How do I check if my GA4 conversion events are set up correctly?
In GA4, go to Admin > Events and confirm the events that matter to your business (purchases, sign-ups, form submits) are marked as conversions. If the list is empty or generic, they're not configured.
Can I recover historical data after fixing a GA4 setup mistake?
Only partially. Retention and custom dimension settings aren't retroactive — data not captured under the old settings is gone. Filtering and conversion fixes apply going forward only.
How often should a GA4 setup be audited?
At minimum, once a year or after any major site or stack change. Teams that skip this tend to discover data problems only when someone asks a question the data can't answer.
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