Migrating to Klaviyo: The ESP Cutover Hub
Choose the right migration path from Omnisend, Constant Contact, Campaign Monitor, HubSpot, Sendlane, or another ESP without losing consent, suppressions, forms, automations, or sender reputation.
- Choose an integration, CSV, or hybrid migration path
- Prove the cutover before retiring the old ESP
Which Klaviyo migration path should you use?
Use a native one-time integration when Klaviyo supports the outgoing ESP and the integration preserves the data you need. Use a controlled CSV migration when no supported integration exists. Use a hybrid when the integration moves profiles and engagement history but leaves consent evidence, suppressions, custom fields, templates, forms, or automation logic behind. The path is less important than the reconciliation: every migration needs a before-and-after control sheet.
Klaviyo currently directs supported providers to dedicated integrations and treats those connections as migration tools, not permanent dual-ESP architecture. For unsupported providers, its guidance is to import contacts and engagement context, import bounces and unsubscribes into suppression, replace every capture path, rebuild autoresponders as flows, and begin with engaged sending.
Choose the migration transport
Validate exactly which lists, suppressions, engagement events, and fields sync; do not assume complete parity.
Separate subscribed, unsubscribed, bounced, and engagement cohorts; preserve consent timestamps and source where available.
Obtain source exports or API access before activating marketing. Never infer consent from presence in a list.
ZHS migration rule: choose the route that preserves authoritative state, then prove counts and behavior before cutover.
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What changes between Mailchimp, Omnisend, Sendlane, and other ESPs?
The control framework stays the same; the transport changes. Mailchimp has a dedicated Klaviyo migration path and can sync more historical context. Other supported tools may have their own integration. An unsupported or partially supported tool relies more heavily on exports, custom properties, and manual evidence.
Migration path comparison
| Criteria | Native integration | CSV import | Hybrid |
|---|---|---|---|
| Best when | Klaviyo documents a supported one-time connector | The old ESP exports clean state and engagement data | The connector and exports each cover different required fields |
| Primary risk | Assuming every field and suppression syncs | Flattening consent and suppression into one list | Creating two conflicting sources of truth |
| Required proof | Connector scope plus reconciled counts | Import mapping plus row-level spot checks | Field-by-field ownership map |
| Cutover rule | Disable duplicate sends after validation | Freeze old sends before activating Klaviyo | Record an explicit owner for every sync and form |
The safest path is the one your team can reconcile, test, and roll back—not automatically the path with the fewest clicks.
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What must be inventoried before any migration?
Inventory people, permissions, behavior, and production assets separately. Profile count alone does not prove that a migration preserved the right to contact someone or the logic that determines what they receive.
ESP migration control sheet
- Subscribed email profiles by list and source
- Email unsubscribes, complaints, bounces, and suppressions
- SMS consent status, timestamp, source, country, and number
- Tags, groups, segments, custom fields, and data types
- 30-, 60-, 90-, and 180-day engagement cohorts
- Active automations, triggers, filters, branches, and exits
- Forms, landing pages, checkout capture, and third-party lead sources
- Templates, reusable blocks, coupons, and dynamic variables
- Sending domains, From addresses, reply-to addresses, and authentication
- Commerce, reviews, loyalty, subscription, support, and analytics integrations
- Baseline delivery, clicks, conversion, unsubscribe, complaints, and attributed revenue
- Cutover owner, freeze window, rollback point, and retirement date
Store source exports unchanged. The control sheet explains them; it does not replace them.
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How should consent and suppressions be transferred?
Preserve channel-specific state. A profile may be subscribed to email, unsubscribed from SMS, bounced on one address, or consented under a particular form and disclosure. Do not merge those states into a single subscribed column. Upload known unsubscribes and bounces to Klaviyo suppression before marketing activation, and spot-check source records against Klaviyo profiles after import.
If the old ESP cannot provide consent evidence, presence in its database is not permission. Isolate ambiguous records and escalate them for a business/legal decision instead of silently marketing to them.
How do you cut over forms, flows, and integrations?
Build Klaviyo destinations before switching traffic. Replace embedded and popup forms, redirect third-party capture, verify checkout subscription behavior, and submit a real test through every source. Rebuild flows from their business logic rather than copying canvas screenshots. Then freeze production edits in the old ESP, record the final export time, apply the delta import, and activate one owner per message.
The controlled cutover
- 01Before freezeBuild and test the destination
Integrations, forms, segments, flows, templates, authentication, and reporting exist in Klaviyo but broad marketing remains off.
- 02FreezeStop structural changes in the old ESP
Record final counts and exports so the reconciliation has a stable source.
- 03DeltaImport new and changed state
Bring over profiles, suppressions, consent, and engagement added after the first migration pass.
- 04ActivateTurn on one owner per journey
Prevent duplicate forms, campaigns, and automations during the transition.
- 05StabilizeRamp engaged audiences and monitor
Compare delivery and conversion with the baseline before expanding volume.
- 06RetireRemove the old connection only after proof
Keep read-only evidence through the validation window, then remove obsolete forms, scripts, and integrations.
A migration ends when Klaviyo is trusted as the source of truth—not when a CSV finishes uploading.
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What proves the migration succeeded?
Reconcile totals by state, not just total profiles. Test capture, consent, suppression, commerce events, flow entry, purchase exits, coupons, links, personalization, and reporting with named test profiles. Confirm no production message can send from both systems. Then compare the first engaged campaigns and core flows against the recorded baseline using the same attribution settings.
For Mailchimp-specific connector behavior, use the Mailchimp-to-Klaviyo migration runbook. For every provider, the ZHS standard is the same: preserve evidence, assign ownership, stage activation, and keep a rollback point until the new system is proven.
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