GA4 migration is no longer optional. Google fully retired Universal Analytics in July 2024, and any business still relying on historical UA data without a properly configured GA4 property is flying blind. But even businesses that technically have GA4 installed often have it set up incorrectly — missing key events, broken ecommerce tracking, no connection to Google Ads, and default settings that filter out valuable data.
This guide covers what GA4 migration actually involves, what most businesses get wrong, and how to ensure your analytics setup is generating the data you need to make informed marketing decisions.
Why GA4 Is Fundamentally Different From Universal Analytics
GA4 is not an upgrade to Universal Analytics. It is a completely different platform built on a different data model. Understanding this distinction is important because it explains why a simple “migration” often is not enough.
Event-based vs session-based. Universal Analytics tracked pageviews and sessions. GA4 tracks events. Every user interaction — a page view, a scroll, a click, a form submission, a purchase — is an event. This gives you more flexibility but requires more deliberate configuration.
Different attribution models. Universal Analytics defaulted to last-click attribution. GA4 uses data-driven attribution across channels. This means your channel performance numbers will look different even if nothing else changed. Do not panic when you compare GA4 reports to old UA reports and the numbers do not match — they are measuring differently, not incorrectly.
User-centric measurement. GA4 focuses on users and their journeys across devices and sessions, not just individual sessions. This is more accurate for modern buyer behavior where someone might discover you on mobile, research on desktop, and convert on a tablet.
Privacy-first design. GA4 was built for a world of cookie restrictions and privacy regulations. It uses machine learning to model conversions when direct measurement is not possible, and it does not store IP addresses by default.
What a Proper GA4 Migration Includes
If your GA4 was set up using Google’s automated setup assistant or a basic tag, you likely have a skeleton installation that is missing critical configuration. Here is what a comprehensive setup covers.
Data stream and property configuration. Enhanced measurement settings reviewed and customized (not just left at defaults). Data retention set to 14 months (the maximum, versus the default 2 months). Google Signals enabled for cross-device tracking. Referral exclusions configured for your payment processors and third-party checkouts.
Custom event tracking. GA4’s enhanced measurement captures basic events automatically (page views, scrolls, outbound clicks, file downloads). But the events that matter most to your business usually need custom configuration: form submissions, phone number clicks, video engagement, add-to-cart actions, checkout steps, and key page interactions. These are set up through Google Tag Manager for flexibility and maintainability.
Conversion configuration. In GA4, any event can be marked as a conversion (called a “key event”). The critical step is identifying which events represent genuine business value and marking only those as conversions. Too many conversion events dilute your data. Too few leave you blind to important user actions.
Ecommerce tracking. If you sell products online, GA4 ecommerce requires a structured data layer that sends product details, transaction data, and funnel step information. The data layer is different from Universal Analytics ecommerce tracking, so existing implementations need to be rebuilt.
Google Ads integration. Linking GA4 to Google Ads enables audience sharing (for remarketing), conversion import (for smart bidding), and unified reporting. This connection is essential if you run any paid search campaigns. Without it, your Google Ads campaigns cannot optimize against your GA4 conversion data.
Looker Studio reporting. GA4’s built-in reporting interface is less intuitive than Universal Analytics was. Most businesses need a Looker Studio dashboard that presents GA4 data in a format that matches how they actually make decisions: channel performance, conversion trends, landing page analysis, and campaign comparisons.
Common GA4 Migration Mistakes
These are the issues I see in nearly every GA4 audit.
Leaving data retention at 2 months. GA4 defaults to 2-month data retention for user-level data. This means Explorations (GA4’s custom reporting tool) only has 2 months of data to work with. Change this to 14 months immediately. Standard reports are not affected, but any custom analysis is crippled by the 2-month default.
Not configuring cross-domain tracking. If your marketing site is on one domain and your checkout or booking system is on another, GA4 treats them as separate sessions by default. This breaks conversion attribution because the original traffic source gets lost at the domain boundary. Cross-domain tracking through GTM ensures the user journey is tracked as a single session.
Relying on GA4 for Google Ads conversion tracking. While you can import GA4 conversions into Google Ads, the recommended approach is to use Google Ads native conversion tracking as the primary source and GA4 conversions as a secondary comparison. Native tracking is faster, more accurate for Google’s bidding algorithms, and less susceptible to ad blockers. For the most complete picture, implement server-side tracking alongside both.
Ignoring internal traffic filtering. GA4 has a built-in internal traffic filter, but it is not enabled by default. Without it, your own team’s website visits inflate your traffic numbers, skew conversion rates, and pollute your audience segments. Define internal traffic by IP address and enable the filter in Data Settings.
No UTM discipline. GA4 relies on UTM parameters for accurate campaign attribution. If your paid campaigns, email marketing, social media posts, and partner links do not use consistent UTM tracking, your channel data is unreliable. Establish a UTM naming convention and enforce it across all marketing channels.
GA4 Features Most Businesses Are Not Using
Audiences for remarketing. GA4 audiences are far more powerful than Universal Analytics segments. You can build audiences based on event sequences (visited pricing page then did not convert within 7 days), predictive metrics (likely to purchase in the next 7 days), and user properties. These audiences sync directly to Google Ads for targeted remarketing campaigns.
Predictive metrics. GA4 uses machine learning to predict purchase probability, churn probability, and predicted revenue for individual users. These predictions power predictive audiences that you can target with ads — showing your Google Ads to people GA4 predicts are most likely to convert.
BigQuery export. GA4 offers free BigQuery integration, which gives you access to raw, unsampled event data. This enables custom attribution models, advanced segmentation, and data warehouse integration that are impossible within GA4’s interface. If your business is data-sophisticated, BigQuery integration is a significant unlock.
Consent mode. For businesses operating in regions with privacy regulations (GDPR, UAE data protection), GA4’s consent mode models conversion data for users who decline cookies. This recovers data that would otherwise be completely lost, improving both reporting accuracy and smart bidding performance.
The Migration Process Step by Step
Step 1: Audit your current analytics. Document what you are currently tracking in your existing analytics setup. List every conversion action, custom event, audience, and integration. This becomes your migration requirements document.
Step 2: Configure GA4 property settings. Data retention, Google Signals, data filters, attribution settings, and cross-domain tracking. These foundation settings affect everything else.
Step 3: Implement tracking via GTM. Set up custom events, conversion tracking, and ecommerce data layer through Google Tag Manager. GTM gives you the flexibility to modify tracking without touching website code.
Step 4: Verify data accuracy. Run GA4 alongside your existing tracking for at least 2 weeks. Compare conversion counts, traffic sources, and user metrics. Investigate any significant discrepancies.
Step 5: Connect integrations. Link GA4 to Google Ads, Search Console, BigQuery, and any other platforms in your stack. Configure audience sharing and conversion import.
Step 6: Build reporting. Create Looker Studio dashboards that replace your old UA reporting. Train your team on the new reports and GA4’s interface.
If you need help with GA4 migration or want a professional audit of your current setup, learn about our GA4 services or get in touch.
Frequently Asked Questions
Is GA4 harder to use than Universal Analytics?
GA4 has a steeper initial learning curve because it uses a fundamentally different data model (event-based instead of session-based). Reports are structured differently, and some familiar metrics like bounce rate have been replaced (with engagement rate). However, once you understand the event-based model, GA4 is actually more flexible and powerful for tracking user behavior. The key is to invest time in setting up custom reports and explorations that match what you used to monitor in Universal Analytics, rather than trying to find the same reports in the same places.
What data did I lose when Universal Analytics was sunset?
If you did not export your Universal Analytics data before Google deleted it, you lost all historical data from that platform. Google permanently deleted UA data in mid-2024. Going forward, GA4 started fresh from whenever your GA4 property was first set up. If your GA4 property was running in parallel with UA before the sunset, you have GA4 data from that point forward. The lesson is to start new analytics implementations early and run them in parallel to build up historical data before any migration deadline.
How do I set up conversion tracking in GA4?
In GA4, conversions are called “Key Events.” Go to Admin > Events, find the event you want to track as a conversion (like form_submit, purchase, or a custom event), and toggle the “Mark as key event” switch. For custom events, you may need to set them up first using Google Tag Manager or the GA4 interface. Make sure you are tracking actual business outcomes (form submissions, phone calls, purchases) rather than engagement events (page views, scroll depth) as key events, to keep your conversion data meaningful.
Should I use GA4 or Google Ads for conversion tracking?
Use both, but for different purposes. Google Ads conversion tracking (via the Google tag) is best for optimizing ad campaigns because it captures more conversion data through Enhanced Conversions and Consent Mode modeling. GA4 is best as your source of truth for cross-channel analysis because it sees all traffic sources, not just Google Ads. Import your GA4 key events into Google Ads as secondary conversions for cross-reference, but let the native Google Ads tag be your primary conversion source for bidding optimization.
What are the most important GA4 settings to configure right away?
Enable Enhanced Measurement (tracks scrolls, outbound clicks, site search, and video engagement automatically). Extend data retention from the default 2 months to 14 months (Admin > Data Settings > Data Retention). Link your Google Ads, Search Console, and BigQuery accounts. Set up key events for your primary conversion actions. Enable Google Signals for cross-device tracking if your privacy policy allows it. These baseline configurations ensure you are collecting comprehensive data from day one rather than discovering gaps months later.
