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Klaviyo to Lemlist integration — real-time, two-way sync

Keep Klaviyo and Lemlist 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 Klaviyo and Lemlist

Stop re-entering the same information in Klaviyo and Lemlist: 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 Tags, Profiles, Lists, Segments in Klaviyo with Unsubscribes, Webhooks, Team Members, Campaigns in Lemlist 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

  • 01 Sync catalog items from an ERP or PIM so product recommendations and back-in-stock flows use current data
  • 02 Sync customer profiles between Klaviyo and the CRM or warehouse so segments can use fields beyond storefront data
  • 03 Mirror campaign performance data into BI tools for outbound reporting across senders
  • 04 Sync replies, opens, and bounces from Lemlist into the CRM so outbound activity shows on lead and contact records

Common sync patterns

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.

Where one tool produces events: mirror them in the other

Payments, replies, messages, or tickets created in one tool can create or update matching records in the other, keeping context in one place.

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

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

What you can sync between Klaviyo and Lemlist

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.

Klaviyo objects Lemlist objects How this pairing syncs
Campaigns Email and SMS sends expose performance data for warehouse-based reporting. Campaigns Outreach campaigns are the container leads are pushed into from CRMs and list-building workflows. Same entity on both sides — records pair one-to-one and field-level changes reconcile in both directions.
Tags Organizational labels on campaigns, flows, and lists support reporting rollups. Unsubscribes Opt-out records propagate to other outreach tools and the CRM for compliance. Tags is specific to Klaviyo and Unsubscribes to Lemlist — each maps to any object or custom field on the other side.
Profiles Person records with arbitrary custom properties are the target for CRM and warehouse-sourced attributes. Webhooks Hook subscriptions define which activity events are pushed to external endpoints. Profiles is specific to Klaviyo and Webhooks to Lemlist — each maps to any object or custom field on the other side.
Lists Static audience memberships sync in from CRMs and forms for targeting. Team Members Sender and seat records map outreach activity to reps in other systems. Lists is specific to Klaviyo and Team Members to Lemlist — each maps to any object or custom field on the other side.
Segments Dynamic audiences are readable so other tools can mirror who qualifies. Leads Per-campaign prospect records sync in from enrichment sources and back out with status. Segments is specific to Klaviyo and Leads to Lemlist — each maps to any object or custom field on the other side.
Events Timestamped behavioral records tied to metrics; external order and product events are pushed in to trigger flows. Activities Engagement records such as opens, clicks, replies, and bounces sync to CRM timelines. Events is specific to Klaviyo and Activities to Lemlist — each maps to any object or custom field on the other side.

How changes propagate between Klaviyo and Lemlist

Each direction of the sync is driven by what the source system can signal and what the destination accepts — detection, delivery, and expected latency below.

Klaviyo Lemlist Sub-second propagation

DetectionKlaviyo notifies Stacksync of record changes through webhook events. Polling on updated timestamps.

DeliveryEach detected change is written to Lemlist through its API, with automatic retries and rate-limit backoff.

Lemlist Klaviyo Sub-second propagation

DetectionLemlist notifies Stacksync of record changes through webhook events. Webhooks on outreach activity events, plus polling.

DeliveryEach detected change is written to Klaviyo through its API, with automatic retries and rate-limit backoff.

Rate-limit considerations

  • Klaviyo: Per-endpoint burst and steady rate limits apply.
  • Lemlist: Subject to the platform's API rate limits.
What ships with Klaviyo ⇄ Lemlist

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

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

Real-time

Two-way sync

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

No-code + pro-code

Workflow automation

Trigger automated workflows whenever Klaviyo or Lemlist 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 Klaviyo or Lemlist record.

Observability

Monitoring

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

Trading partners

EDI

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

How the Klaviyo and Lemlist connectors work

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

Lemlist

Integration surface
REST API
Authentication
API key
Change detection
Webhooks on outreach activity events, plus polling
Capabilities
read · write · webhooks
Rate limits
Subject to the platform's API rate limits
How it works

How to connect Klaviyo to Lemlist — 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 Klaviyo and Lemlist 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
    Klaviyo connected
    Lemlist connected
    OAuth 2.0
    SSH tunnel
    SSL certificate
    VPC peering
  2. 02

    Choose tables

    Pick the Klaviyo and Lemlist 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 · Klaviyo ⇄ Lemlist
    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
    Klaviyo Lemlist
    Company company_name text
    Email email text
    Amount amount numeric
    Created created_at timestamp
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FAQ

Klaviyo and Lemlist integration FAQ

SECURITY

Security teams trust 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
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 Klaviyo and Lemlist.

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