01 — UA is dead, default GA4 is almost useless
Universal Analytics stopped collecting data on July 1, 2023. Historical data was wiped in free properties on July 1, 2024. If you still see a UA-XXXXX tag in your site code, you have been not-tracking for almost 3 years.
Almost every site has done something: a GA4 property created in a hurry in 2023, a tag inserted, end of story. That "something" is almost useless. Without configured events, declared conversions, extended retention, Consent Mode, the dashboard only shows generic pageviews. When marketing asks "which ad converted?", the consultant answers "I don't know, GA doesn't say".
A well-done GA4 migration is not "moving the tag". It is configuring an analytics system that lets you make decisions: which traffic source brings real customers, which ad burns money, which funnel page loses conversions, which device fails. Without this, marketing is pure gut feeling.
02 — 4 typical problems I see in existing setups
- 01 — Problema
Still on Universal Analytics
Universal Analytics stopped collecting data on July 1, 2023. Historical data was wiped in free properties on July 1, 2024. If you still see a 'UA-XXXXX tag' in the site code, you are simply tracking nothing. Nada. Zero. For almost 3 years.
- 02 — Problema
GA4 imported in 5 minutes
Almost every site has GA4 'something': property created in a rush, tag inserted, end of story. Result: zero custom events, 2-month retention (default), no internal traffic filter, conversions never declared. The dashboard shows pageviews and that's it. You don't know what converts.
- 03 — Problema
Cookie banner that turns everything off
Cookie banner badly configured: without explicit consent, GTM doesn't fire, GA4 receives nothing, Google Ads doesn't see conversions. 40-60% of EU visitors click 'reject' or ignore the banner — that 40-60% becomes invisible. Consent Mode v2 modeled conversions never enabled.
- 04 — Problema
No setup documentation
GTM container with 30+ tags accumulated over years, random naming ('test_2024', 'click-cta-3'), zero docs. Whoever takes over spends weeks figuring out what does what. Often everything gets rebuilt from scratch because it's faster than reverse engineering.
03 — 6-step migration
- 01
Audit current setup
I check what's there: residual UA to remove, existing GA4 property (if any) to clean or rebuild, GTM container to organise. I identify what's worth saving and what to rebuild.
- 02
Map business-driven events
30-minute session to define what matters: macro-conversions (purchase, lead form, booking), micro-conversions (add_to_cart, scroll 75%, time on key page), critical traffic sources. Map events BEFORE touching code.
- 03
Clean GA4 property
New property or cleanup existing: data stream configured, internal traffic filter, cross-domain tracking if needed, debug mode, retention 14 months (max non-paid), enhanced measurement enabled on the right events.
- 04
Organised GTM container
GTM container with logical folders by type (Analytics / Ads / Conversion API), clear naming convention (TY1-Pageview, AY2-Click-CTA, EY3-Form-Submit), reusable triggers, centralised variables. Documentation in spreadsheet.
- 05
Consent Mode v2 (GDPR)
Cookie banner integration (Cookiebot / Iubenda / custom) with Google Consent Mode v2. Tags active even before consent in "modeled" mode (Google reconstructs missing conversions). Full tracking after explicit accept. Test via GA4 DebugView.
- 06
Looker Studio dashboard
Custom dashboard showing only what matters: traffic source by conversion, checkout/lead funnel, top-performing pages, on-site searches, device + region. Single page readable in 5 minutes, daily refresh, shared team access.
04 — Consent Mode v2 + GDPR (the most ignored part)
Consent Mode v2 is the piece most GA4 installers skip. And it's exactly where 40-60% of data is lost in EU markets.
Without Consent Mode v2: the cookie banner completely blocks GTM until the user clicks "accept". Whoever clicks "reject" or ignores the banner is not tracked at all. Result: dashboard shows only 40-60% of real traffic, and decision-makers see only half the truth.
With Consent Mode v2: Google tags receive signals even before consent (in "modeled" mode — anonymous aggregated data, GDPR-compliant). Google uses those signals to reconstruct missing conversions via machine learning. Result: 75-90% of real traffic visible in dashboard, and Google Ads optimisation that works instead of degrading.
Setup requires integration between cookie banner (Cookiebot / Iubenda / custom) and GTM with the 4 correct consent states (ad_storage, analytics_storage, ad_user_data, ad_personalization).
Every project includes this step as standard, never optional.
05 — 5-minute readable Looker Studio dashboard
Native GA4 dashboards are built for analytics experts, not for whoever has to decide whether to spend another 500€ in Google Ads this week. You need custom dashboards that answer specific questions.
Looker Studio (formerly Data Studio) is free, natively connects to GA4 + Google Ads + Search Console + Sheets, and produces single-page dashboards with the KPIs your business needs. Each client gets a personalised dashboard:
- E-commerce: funnel view item → add to cart → begin checkout → purchase, AOV by source, top products, conversion rate per device.
- Lead gen: form submit by source, form abandonment rate, time-to-form per landing page, traffic source quality (qualified leads vs raw leads).
- Content / blog: top articles by traffic + engagement, scroll depth, source per category, on-site searches with frequency.
Automatic daily refresh, team access via shared link, exportable to PDF for monthly reviews. No decorative "executive report": only the numbers that make you act.
06 — FAQs
Do I really need to migrate if Universal Analytics stopped working in 2023?
Universal Analytics hasn't collected data since July 2023, and historical data has already been wiped in free properties since July 1, 2024. If you still have UA installed it's dead code — does no harm, but is useless. The question isn't 'should I migrate' but 'should I finally have analytics that works'. Yes.
Can I recover Universal Analytics historical data?
Only if you exported it before the wipe (Google gave 18 months notice). For those with historical exports (CSV, BigQuery sync, GA Universal API extracts), they can be imported into Looker Studio as a comparison dataset. For those who didn't export, pre-2023 data is lost. Period.
Are GA4 and GTM free?
Yes, both free for most sites. Standard GA4 has limits (10M events/month, 14 months retention, 200 conversion events) but they're sufficient for 95% of cases. GA4 360 (paid, from $50k+/year) is only for enterprise with billions of events. GTM is completely free with no significant limits.
Is Consent Mode v2 actually mandatory?
For Google Ads in EEA + UK it's mandatory since March 6, 2024 — without Consent Mode v2 campaigns don't see conversions and automatic optimisation degrades. For GA4-only setups, it's not strictly 'mandatory' but it's the correct GDPR-compliant practice. I always set it up as standard.
How long does the full migration take?
Depends on site complexity and events to configure. Brochure site with contact form: 1-2 days. E-commerce with checkout, filters, account area: 1-2 weeks. SaaS with internal dashboard and custom tracking: 2-4 weeks. The first audit clarifies real scope.
What happens to my existing Google Ads and Meta Pixel tags?
They get moved to GTM if not already there, with unified Consent Mode v2 setup. Google Ads conversion tracking upgraded to Enhanced Conversions (server-side hashing). Meta Pixel + Conversion API server-side to bypass iOS 14.5 and ad blockers. TikTok, LinkedIn, Pinterest if in use: same pattern. Everything via GTM with consent gating.
Can I add new events after setup, on my own?
Yes, if they're variants of existing events (e.g. duplicate a 'click button' trigger for a new CTA). The documentation I deliver explains the pattern. For more complex new events (e-commerce purchase with custom line items, multi-step events), quarterly retainer or on-demand intervention makes more sense.