How to Integrate OptiMonk with Klaviyo

OptiMonk no longer asks for Klaviyo public and private API keys. As of the April 2026 help article, you authenticate with OAuth, pick a list and map fields. Older screenshots of Create Private API key are out of date. Do not paste keys.

Once this is on, a form fill on the campaign adds the person to the Klaviyo list you chose.

Connect a campaign

1. Log in at app.optimonk.com/login/en.
2. Campaigns → open the campaign.
3. Edit settings.
4. If OptiMonk already sees Klaviyo on the site, click Select on the Klaviyo suggestion. Otherwise Add new integration and pick Klaviyo.

5. Click Authenticate. You go to Klaviyo, pick the account, and allow OptiMonk to read lists and segments.
6. You land back in OptiMonk. Name the integration. Next.
7. Choose the Klaviyo list the campaign should write to.
8. Map fields. Email, first name, last name, phone, coupon code, custom fields. Default identifiers include email, first_name, phone_number, address fields and a checkbox.

9. Done, then Next.

A coupon shown on the campaign can go to Klaviyo as a custom property, which you then drop into a flow. That is the useful part for a "here is 10% off" popup.

Double opt-in and SMS consent

Double opt-in is a switch on the Klaviyo integration. If it is on, Klaviyo only accepts the person after they confirm the follow-up email. Turn it off only if your country does not require it; Klaviyo's own double-opt-in guide is the rulebook.

Phone numbers can go to Klaviyo with SMS consent. In the US and Canada, OptiMonk says that consent is enough for SMS to start. UK and Australia need an alphanumeric sender ID on the Klaviyo SMS plan. Show terms and a privacy link on the popup when you collect a number.

If the list does not update

Check field mapping (email must map to email). Confirm you authenticated the right Klaviyo account. Trigger the campaign that has the integration, not a different one. OptiMonk support and the Klaviyo article are the next stop.

Other ESP guides: OptiMonk integrations.