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Customer.io to Klaviyo integration — real-time, two-way sync

Keep Customer.io and Klaviyo in sync without custom scripts. Cut weeks of integration work, eliminate silent data drift, and give your team a single, reliable source of truth.

  • SOC 2 and 6 other compliance frameworks
  • POC with real engineers in minutes

Adopted by fast-scaling companies moving mission-critical data in real time

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Why teams connect Customer.io and Klaviyo

Stop re-entering the same information in Customer.io and Klaviyo: Stacksync keeps the records they share consistent in real time, in both directions.

Two tools in the daily stack often hold overlapping information: the same people, the same companies, or the same pieces of work, described twice. The tools do different jobs, so consolidating is not the answer; the overlap just needs to stop drifting.

Stacksync syncs People, Objects, Events, Segments in Customer.io with Events, Metrics, Campaigns, Flows in Klaviyo in real time. You choose which records overlap, map the fields that should match, and pick a direction or let changes flow both ways. From then on, an update made in either tool is reflected in the other within seconds, without exports or copy-paste.

Because the sync is field-level, each tool keeps its own extras; only the shared data is held in agreement.

Common use cases

  • Land delivery and engagement events (sent, opened, clicked, bounced) from reporting webhooks into a warehouse for attribution analysis.
  • Keep unsubscribe and subscription-preference state consistent between Customer.io and the CRM to avoid compliance gaps.
  • Push offline, ERP, or subscription order events into Klaviyo as metrics to trigger post-purchase and win-back flows
  • Mirror campaign and flow engagement events into a warehouse for revenue attribution alongside order data

Where Klaviyo is where the team documents or plans: keep its data fed

Information that originates in Customer.io stays current in Klaviyo instead of going stale after a one-time paste.

Handoffs between teams

When work started in one tool continues in the other, the shared fields travel with it automatically.

Where both tools track people or companies: one consistent record

Contact and company details corrected in either tool update the other, so nobody works from the old version.

What you can sync between Customer.io and Klaviyo

Representative objects on each side — any object or custom field can map to any target. Schemas are auto-detected; types are converted between the two systems.

Customer.io objects Klaviyo objects
Newsletters Recurring email sends with performance metrics available for reporting syncs. Lists Static audience memberships sync in from CRMs and forms for targeting.
People Profiles with attributes, matched on identifiers like id or email; the main write target of data syncs. Segments Dynamic audiences are readable so other tools can mirror who qualifies.
Objects Non-person entities such as accounts or companies, related to people for account-level messaging. Events Timestamped behavioral records tied to metrics; external order and product events are pushed in to trigger flows.
Events Behavioral events sent via the Track API that trigger campaigns. Metrics Event type definitions organize the activity stream used in segmentation and attribution.
Segments Attribute- or event-based groups; data syncs feed the attributes segments evaluate. Campaigns Email and SMS sends expose performance data for warehouse-based reporting.
Campaigns Automated workflows whose membership and metrics can be read via the App API. Flows Automation definitions and their engagement data sync outward for attribution.
What ships with Customer.io ⇄ Klaviyo

Connect Customer.io and Klaviyo for flexible, real-time data sync.

Real-time sync, workflow automation, event queues, EDI, and monitoring, for every Customer.io–Klaviyo connection.

Real-time

Two-way sync

Changes in Customer.io or Klaviyo instantly reflect in both systems. No stale data, no manual imports.

No-code + pro-code

Workflow automation

Trigger automated workflows whenever Customer.io or Klaviyo data changes, update records, fire webhooks, or kick off sequences without brittle API scripts.

At scale

Event queues

Handle millions of events per minute without losing a single Customer.io or Klaviyo record.

Observability

Monitoring

Track your Customer.io ⇄ Klaviyo sync health, view errors, and replay failed events in one click.

Trading partners

EDI

Transform legacy EDI complexity into simple database interactions between Customer.io and Klaviyo.

How the Customer.io and Klaviyo connectors work

Customer.io

Integration surface
REST APIs split by purpose: Track API for data ingestion, App API for campaigns, people lookups, and messages
Authentication
Basic auth with site ID and API key for the Track API; bearer token for the App API
Change detection
Reporting webhooks push message and delivery events; person attribute changes are not streamed and require source-side detection
Capabilities
read · write · webhooks
Rate limits
Subject to per-API rate limits documented by Customer.io

Klaviyo

Integration surface
REST API compliant with the JSON:API specification
Authentication
OAuth 2.0 for apps or private API keys
Change detection
Polling on updated timestamps; outbound webhooks exist for event topics (availability depends on plan or app-partner status) and as flow webhook actions
Capabilities
read · write · webhooks
Rate limits
Per-endpoint burst and steady rate limits apply
How it works

How to connect Customer.io to Klaviyo — three steps, no code

Configure and sync within minutes, no code. Whether you sync 50k or 100M+ records, Stacksync handles the queues, infra, and plumbing. Integrations are non-invasive and need zero setup on your systems.

  1. 01

    Connect your apps

    Authenticate Customer.io and Klaviyo with each platform's native method — OAuth, API keys, or service accounts — plus secure options like SSH tunneling, IP whitelisting, and VPC peering.

    • OAuth 2.0
    • SSH tunnel
    • VPC peering
    Customer.io connected
    Klaviyo connected
    OAuth 2.0
    SSH tunnel
    SSL certificate
    VPC peering
  2. 02

    Choose tables

    Pick the Customer.io and Klaviyo objects to sync — Stacksync auto-detects both schemas, including custom fields where the platform exposes them. Sync to existing tables, or let Stacksync create new ones with ideal data types.

    • Standard objects
    • Custom objects
    • Auto-schema
    objects · Customer.io ⇄ Klaviyo
    Customers 12,480
    Sales Orders 8,213
    Invoices 5,902
    Items 1,344
  3. 03

    Map fields

    Fields map automatically even when names and types differ. Stacksync handles transformation and type casting for you, zero configuration required.

    • Auto-map
    • Type casting
    • Transforms
    Customer.io Klaviyo
    Company company_name text
    Email email text
    Amount amount numeric
    Created created_at timestamp
Try interactive demo
FAQ

Customer.io and Klaviyo integration FAQ

SECURITY

Security teams love Stacksync

As a data company, we understand the importance of keeping your data secure. Stacksync is built with security best practices to keep your data safe at every layer, and is DPF-certified for US, EU, UK and CH data transfers.

Learn more about security
SOC 2 type II
ISO 27001
HIPAA BAA
GDPR
CCPA
CSA STAR
DPF US-EU-UK-CH
→ SECURITY WITH BENEFITS

SSO & SCIM

Let your users access Stacksync from your centralized user management systems. Works with Okta, Azure, Google SSO and more.

Alerts

Immediately get alerted about record syncing issues over email, Slack, PagerDuty and WhatsApp. Resolve issues from a centralized dashboard with retry and revert options.

Secure connection options

Securely connects to your systems with:

OAuth 2 SSH Tunnelling SSL certificates IP Whitelisting VPN gateway VPC peering and more

Related integrations

Every pair below is a real-time, two-way sync. Search all 386 integrations available for Customer.io and Klaviyo.

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