CMP migration: changing Consent Management Platform without breaking tracking

Migrating from one Consent Management Platform to another — typically tarteaucitron to Axeptio, or Cookiebot to Didomi for enterprise reasons — is a sensitive engagement. Done badly: Consent Mode v2 breaks during transition, Google Ads modeled conversions lost, CNIL notice received, inconsistent consent history. Done well: invisible from the user side, with clean Consent Mode v2 alignment and improved acceptance rate. My CMP migration fee: €3,800 for ~6 consulting days, delivered in 4 weeks.

Five most common migration cases

tarteaucitron → Axeptio (case #1 in France). For sites moving from open-source to commercial FR solution with native Consent Mode v2 support.

tarteaucitron → Cookiebot (case #2). For multilingual sites needing 35+ language support.

Cookiebot → Didomi. For groups wanting advanced multi-brand governance.

OneTrust → Axeptio or Didomi. For organizations reducing enterprise OneTrust costs.

Custom internal → standard CMP. For organizations maintaining their own solution wanting to return to standard.

Why migrate

Consent Mode v2 support missing (tarteaucitron). CNIL and market recognized tarteaucitron lacks official Consent Mode v2 support. Compatibility must be hand-coded on top.

Design or UX no longer converting. 2018-2020 CMP banners often suffer from dated design or UX that discourages acceptance. A modern CMP with optimized design typically lifts acceptance 8-20 points.

Cost no longer justified (OneTrust for SMBs). OneTrust is excellent in enterprise governance but oversized for mid-market sites. Migration to Axeptio or Cookiebot divides cost by 5-10x.

Migration method

Phase 1 — Current CMP audit (1 day)

Inventory: declared cookie categories, Consent Mode v2 mapping, observed acceptance rate, available history recovery mechanism, GTM integrations.

Phase 2 — New CMP selection and provisioning (1 day)

CMP choice with you, account creation, category configuration, GDPR-compliant banner design.

Phase 3 — Consent history recovery (1 day, if applicable)

Variable compatibility:

• tarteaucitron → Axeptio: no native recovery (different cookies)
• Cookiebot → Didomi: recovery possible via custom CSV export
• Didomi → Cookiebot: native recovery possible
• OneTrust → Didomi: recovery via OneTrust API + Didomi import

If impossible, users notified proactively (info page, email).

Phase 4 — Parallel deployment (2 days)

7-14 days, old and new CMP coexist (new takes over, old dormant). Validate:

• Consent Mode v2 signals send correctly
• Acceptance rate measured and compared
• GA4/Google Ads tracking works normally
• No third-party pixel loads before consent

Phase 5 — Old CMP shutdown + documentation (1 day)

Once new CMP stable, uninstall old (legacy cookie deletion, source code removal, privacy policy update). Shared Notion with final architecture.

Concrete cases

Premium ecommerce €5M revenue: tarteaucitron → Axeptio migration. 5 days, 3 weeks. Result: acceptance from 52% to 67%, +14% Google Ads modeled conversions in following 60 days.

Multilingual media (FR, EN, DE, ES): tarteaucitron → Cookiebot migration. 6 days, 4 weeks. Native Consent Mode v2 conformity, multilingual support automatic.

Multi-brand retail group (4 sites): Cookiebot → Didomi migration for centralized governance. 10 days, 6 weeks. Single dashboard for 4 brands, listing-compliant audit trail.

Frequently asked questions

Migration duration?

Standard: 4 calendar weeks (6 consulting days). Multilingual or multi-domain sites: 6-8 weeks. Multi-brand groups with complex governance: 8-12 weeks.

SEO risk?

Marginal. The CMP banner renders client-side after initial HTML — invisible to Googlebot fast crawl. SEO not affected typically.

Consent history?

Depending on source/target CMPs. When native recovery is possible, used. Otherwise, users notified and banner reappears for 1-2 months for return visitors.

Notify CNIL?

Not systematically. CNIL doesn’t approve CMP changes. But processing register must be updated, and privacy policy must mention new CMP.