GA4 Migration: The Mistakes Most Sites Made (and How to Fix Them)
Photo by Deng Xiang on UnsplashMost GA4 migrations were rushed when Universal Analytics shut down, leaving conversions mistracked, key events missing, cross-domain tracking broken, and no server-side tagging. The fix is a structured audit: verify key events and conversions actually fire, rebuild missing event tracking, set up cross-domain and server-side tagging, then reconcile GA4 numbers against real CRM or revenue data.
- ✓GA4's event-based model is fundamentally different from UA — old goals don't map over automatically.
- ✓The most common failures: key events never configured, so the data that actually drives decisions is missing.
- ✓Cross-domain tracking is routinely skipped, splitting one customer journey into phantom sessions.
- ✓Always reconcile GA4 conversions against CRM or Stripe — if the numbers don't match, something is wrong.
Why so many GA4 setups are quietly broken
When Universal Analytics stopped processing hits in July 2023, most teams scrambled to get something live. The default GA4 property records page views and some automatic events out of the box — so it looks like it's working. But looking like it's working and actually tracking the things that matter are two very different states. I audited a B2B SaaS company's GA4 in early 2024 and found their 'contact form submitted' key event had never fired once. They had six months of data showing zero form conversions in analytics — while their CRM had 340 leads. Nobody had noticed because nobody had checked.
The five most common gaps I find in audits
- 01Key events (conversions) never configured — GA4 doesn't know what your business goals are unless you tell it explicitly. No one told it.
- 02Critical interactions never set up as events — form submissions, phone call clicks, add-to-cart, file downloads — all the things you actually care about.
- 03Cross-domain tracking broken — if your checkout is on a subdomain or third-party cart, GA4 is splitting every purchase into two sessions and misattributing everything.
- 04No server-side tagging — so iOS 14 and ad blocker losses go unmeasured, making data look complete when it isn't.
- 05Numbers never reconciled against real revenue — so the gaps went unnoticed for months.
How to audit and fix it
Start by listing the five most important actions a visitor can take on your site. For each one: does it fire as a GA4 event? Is it marked as a key event? Does the volume roughly match what your CRM or payment processor shows? Any gap is a tracking failure. Fix them in order of business impact — the form submission tracking matters more than scroll depth.
An analytics setup you don't trust is worse than no analytics at all. You make the same confident decisions either way — but one set is based on lies.
The reconciliation step most people skip
After fixing the event tracking, compare GA4's key event count against your CRM, Stripe, or booking system for the same period. A 10–15% gap is normal (attribution differences, offline conversions). A 40%+ gap means something is still broken. This reconciliation step is what separates a GA4 setup you can make decisions on from one that just looks like data.
Is GA4 hard to set up correctly?
The basic install takes 10 minutes. A correct, decision-grade setup — with proper event tracking, key events, cross-domain configuration, consent mode, and server-side tagging — takes days and requires deliberate planning. Most teams have the first and not the second.
How do I know if my GA4 is tracking correctly?
Reconcile GA4 key event counts against your actual business numbers — CRM leads, Stripe payments, booking confirmations. Persistent gaps of 20%+ mean missing events or attribution loss. Use GA4's DebugView and GTM preview mode to trace specific conversions end to end.
Do I still need GA4 if I have server-side tracking?
Yes — they do different jobs. GA4 is your analytics and reporting layer for understanding user behaviour, content performance, and attribution. Server-side tracking improves the accuracy of both GA4 and your ad platform conversions. You need both working together.
Want this kind of system built for your business? Let's talk — the first call is free, no pressure.