Klaviyo Vol 5: Solving Localised Double Opt-In at Scale

Shopify Markets simplifies international commerce by bringing multiple countries into a single store and operating model.

However, when it comes to email consent and localisation, that simplicity introduces new considerations. When subscribers sync from Shopify to Klaviyo, they enter a single list with a single language and consent experience. While this works well for single-market brands, it becomes more complex when operating across markets like Belgium, Germany, France, and Spain.

This is exactly what we discovered while working on the Shopify Markets x Klaviyo setup for Meyer/MMX. What started as a standard integration quickly exposed a gap that neither platform solves natively, and we had to engineer our way around it.

The Problem

Shopify Markets centralises all international traffic into one Shopify store. From a commerce perspective, that's powerful. From a consent and lifecycle perspective, it creates friction you can't ignore.

Shopify can only sync subscribers into one primary Klaviyo list.

When Shopify syncs subscribers to Klaviyo, everyone, regardless of country or language, goes into one default list. That list can only have one subscription source, one consent experience, and one language for the double opt-in page and email.

This immediately becomes a problem when customers are signing up from different markets expecting communications in their own language.

Market-specific consent requires localised double opt-in.

Markets across Europe don't just prefer localised consent, they often require it. Different languages, sometimes different legal wording, and often different expectations around confirmation. 

Klaviyo won't re-trigger double opt-in for "already subscribed" profiles.

Here’s the real blocker. When a subscriber enters Klaviyo via a single opt-in source, or has already confirmed their subscription, they’re immediately marked as subscribed. If that profile is later moved to another list, Klaviyo won’t re-trigger the list-specific double opt-in email.

The result? Customers were entering a global list with a single-language consent experience, never receiving the correct market-specific double opt-in, and creating compliance risk alongside a broken onboarding experience.

This wasn't a configuration mistake. It's simply how the platforms behave, and we needed to work around it.

The Fix

To fix this, we had to stop relying on default platform behaviour and engineer our own consent routing logic.

Enrich customer profiles with market and language data

First, we needed reliable detection. We added custom Shopify properties that get passed to Klaviyo: Market (e.g. BE, DE, FR), and Locale/browsing language (e.g. fr-BE, nl-BE, de-DE). These properties became the foundation for precise segmentation and routing.

Set the global Shopify-synced list to single opt-in.

Because the sync settings only allow one list with a single language to be connected to Shopify consent pages, we intentionally converted the global synced list to single opt-in. This allowed subscribers to enter Klaviyo immediately, avoided sending the wrong-language double opt-in, and gave us control to trigger the correct consent later. This wasn't about bypassing compliance, it was about sequencing it correctly.

Build a list update flow with conditional logic.

Once a subscriber entered the global list, a dedicated List Update Flow took over. The flow reads the Market and Locale properties, routes the subscriber through a detailed conditional split tree, and identifies the exact combination (e.g. BE-FR, BE-NL, DE, FR). When a match is found, the flow sends a webhook.

Use webhooks to override status and trigger the right double opt-in.

The webhook performs the critical step Klaviyo doesn't support natively. It overrides the subscription status and moves the profile into the correct market-specific list. Because that list is configured with its own language, legal copy, and double opt-in settings, the subscriber receives the correct confirmation email, in the correct language, for the correct market.

Results and Takeaway

This approach enabled accurate list assignment for every subscriber, fully localised double opt-in across all markets, and a consistent, compliant onboarding experience. It also created a scalable framework that supports new countries and languages without rework—all while maintaining a single Shopify store and a single synced Klaviyo list.

International growth isn't just about currency and shipping. Consent, language, and customer experience matter just as much.

By combining Shopify customer property enrichment, a single-opt-in global entry point, conditional Klaviyo flows, and webhook-driven list reassignment, we created a market-specific, language-correct double opt-in system—something neither Shopify Markets nor Klaviyo currently supports out of the box.

This approach turns Shopify Markets into a truly scalable foundation for international brands using Klaviyo, without compromising compliance or customer experience.

Frequently Asked Questions

What is the problem with Shopify Markets and Klaviyo consent?

Shopify Markets centralises all international traffic into one store, but Shopify can only sync subscribers into a single Klaviyo list with one language and one consent experience. For multi-market brands, that means customers may never receive the correct market-specific, localised double opt-in.

Why won't Klaviyo re-trigger double opt-in for existing profiles?

Once a subscriber enters Klaviyo through a single opt-in source or has already confirmed, they are marked subscribed. If that profile is later moved to another list, Klaviyo does not re-trigger that list's double opt-in email, which breaks localised consent for multi-market brands.

How do you set up localised double opt-in across markets in Klaviyo?

Enrich Shopify profiles with market and locale properties, set the global synced list to single opt-in for immediate entry, then run a list-update flow with conditional logic that reads those properties and fires a webhook to override status and move each subscriber into the correct market-specific list.

Can you run market-specific consent with a single Shopify store and Klaviyo list?

Yes. By combining Shopify customer-property enrichment, a single-opt-in global entry point, conditional Klaviyo flows, and webhook-driven list reassignment, you can deliver language-correct double opt-in per market while keeping one Shopify store and one synced list, something neither platform supports natively.