GA4 migration. Move from UA without losing reporting continuity - validate data before cutover, not after.

GA4 Migration End-to-end consulting and implementation

I run GA4 migrations with GTM Server-Side, BigQuery and Looker Studio - reports work from day one

UA is gone and GA4 is "somewhere there" - but conversions do not match, events disappeared and the team does not know which report is true. Moving to GA4 without a plan risks data loss and broken reporting. I run migrations using dual tagging → validation → cutover: UA→GA4 event mapping, parallel operation of both systems, data comparison, then UA shutdown - with GTM Server-Side, BigQuery, Consent Mode v2 and Looker Studio.

Book a consultation Check GA4 status

Does this sound familiar?

UA switched off, GA4 "sort of works"

Migration "done" by a developer, but data does not match reality.

Year-over-year comparisons impossible

No continuity between UA and GA4 data - YoY reports make no sense.

UA events have no GA4 equivalents

Goals, custom events, e-commerce - UA→GA4 mapping was never done.

Dual tagging without validation

UA and GA4 run in parallel, but nobody compares data before cutover.

Team unsure which report is "true"

Old UA reports in Looker, new ones in GA4 UI - chaos and lost trust in data.

BigQuery not enabled from GA4 day 0

Months of raw data lost - historical analysis cannot be rebuilt.

How migration works - 4 steps

  1. 01

    UA audit and mapping

    Inventory of UA tags, goals, custom events and dimensions. UA→GA4 mapping with gap documentation.

    Deliverable: UA→GA4 migration map + gap analysis
  2. 02

    Dual tagging and parallel run

    New GA4 property, UA+GA4 running in parallel, daily comparison of key metrics for 2–4 weeks.

    Deliverable: UA vs GA4 comparison report
  3. 03

    Target stack: GTM, sGTM, BigQuery

    Server-side tagging, Consent Mode v2, BigQuery export from day 0, Looker Studio with reporting continuity.

    Deliverable: GTM + sGTM + BigQuery + dashboards
  4. 04

    Cutover, validation, training

    UA shutdown after positive validation, end-to-end tests, documentation and team training on the new stack.

    Deliverable: go-live + documentation + training

What you get

UA audit and event mapping

Inventory of current UA analytics: tags, goals, events, dimensions. Full UA→GA4 map with priorities.

Goals → conversions Event mapping Gap analysis

Dual tagging and parallel run

Parallel UA+GA4, data comparison, variance report - cutover only after validation.

Dual tagging Validation Parallel run

GA4, GTM Server-Side

New GA4 property, GA4 e-commerce schema, server-side tagging, first-party cookies.

GA4 property sGTM E-commerce

BigQuery and Consent Mode v2

Raw data export from migration day 0, retention, CMP integration, GDPR compliance.

BigQuery Consent Mode GDPR

Looker Studio - reporting continuity

New dashboards mirroring former UA reports, connected to GA4 and BigQuery.

YoY continuity Dashboards BigQuery

Cutover and handover

Go-live, UA shutdown, QA tests, migration documentation and team training.

Go-live QA Training
  • For whom: companies on Universal Analytics or with an unfinished GA4 migration that need an ordered stack and reporting continuity.
  • Model: one-off migration (6–10 weeks depending on UA complexity); optional analytics retainer for post-cutover support. Fresh implementation? See GA4 implementation.
  • Outcome: one consistent GA4 system with validated data, BigQuery from day 0, cookieless readiness - no reporting "black hole" after migration.

Free tools - start on your own

Check current GA4 status, estimate BigQuery costs or deepen your knowledge before discussing migration.

GA4 Configuration Auditor

Check what already works in GA4 after migration - configuration, events, e-commerce and common errors.

Run auditor

BigQuery Calculator

Estimate GA4 export costs to BigQuery - plan storage and query budget at migration stage.

Calculate costs

GA4 Events Encyclopedia

UA vs GA4 differences, new events, parameters and reports - complete migration reference.

Browse encyclopedia
Krzysztof Surowiecki

Krzysztof Surowiecki. I have led dozens of UA → GA4 migrations - I know which events have equivalents, where data diverges and how to preserve reporting continuity while both systems run in parallel.

  • UA → GA4 mapping: goals, events, custom dimensions - nothing disappears without a conscious decision.
  • Dual tagging and parallel run - data comparison before cutover, no surprises after UA is switched off.
  • BigQuery from day 0 of migration - GA4 raw data preserved for years, not just 14 months in the UI.

Trust - why clients rely on me for analytics

20+years of experience
150+projects
50+clients
7expert tools
  • One accountable person: no hand-offs between departments - you work directly with me.
  • Consulting-first approach: UA audit and migration plan before code - cutover only after data validation.
  • Confidentiality and security: NDA and work standards suited to data-sensitive organisations.

Contact - let's take the first step

Tell me about your current UA/GA4 stack, data issues after migration and reporting requirements. On the call I will plan migration scope, dual tagging and cutover timeline.

  • Discussion about current UA/GA4, GTM tags and reporting needs (YoY, e-commerce, campaigns).
  • Recommendation: UA audit, event mapping, parallel run plan and cutover.
  • Quote, timeline and post-migration support model.
Book a consultation Pre-migration audit