How we doubled our conversion rate using Klaviyo audience sync in Meta ads

As digital marketing manager at swimwear brand Kulani Kinis, I’m always looking for ways to communicate with our shoppers on a more personal level—via not only owned channels, but paid ads as well.

When I first pitched the idea of creating hyper-specific segments for our back-in-stock paid campaigns, I wasn’t entirely sure what to expect. But the results spoke for themselves: we doubled our conversion rate by integrating Klaviyo audience sync with Meta advertising.

Here’s how we did it, what we learned, and why this approach could transform your paid media strategy.

The challenge: making paid media more personal

Most brands cast a wide net with their retargeting campaigns. It’s a tactic Anna Sophie Fokdal Christensen, head of email and retention at FABO, a holistic growth partner for ecommerce brands based in Denmark, cautions against.

“Nothing feels more impersonal than an ad targeted at the wrong moment,” she says. “With some brands, a shopper could get bombarded with paid ads all over the internet after filling out a customer support form. And just like that, the relationship is hanging by a thread, all because the brand wasn’t careful about excluding service inquiries from their paid ad send.”

Christensen is right: brands make big mistakes with under-personalizing paid ads.

We wanted to test ultra-personalized paid ads: what if we could target people with the exact products they’d already expressed interest in?

At Kulani Kinis, we launch collections during key peak summer periods in the year, and we noticed customers signing up for back-in-stock notifications on specific designs. This gave us a goldmine of intent data that we weren’t fully using in our paid advertising.

The test set-up

We decided to focus on 4 specific prints from our recent collections, ranging from newer releases to designs that had launched several months earlier. The test ran for 10 full days in March, targeting both the US and European markets.

Creating the segments

In Klaviyo, I created individual segments for each print. The process was straightforward:

1. First, we set our segment definition: people who subscribed to back-in-stock notifications for specific prints in the last 30 days.
2. Next, we cloned each segment and layered on a second condition: placed an order during the testing period.
3. This allowed us to track conversions at a granular level.

Integration with Meta

The real magic happens through Klaviyo’s Meta integration. Any segment created in Klaviyo can be pushed directly into Meta Ads, where it matches profiles based on email addresses. This creates highly targeted audiences that would be impossible to build natively in Meta.

With the Klaviyo x Meta integration, Christensen and her team at FABO have the transparency they need to:

• Track performance in real-time.
• Calculate ROAS per audience and campaign.
• Fine-tune targeting based on actual customer behavior.
• Remove friction that could potentially damage the brand, like showing ads to recent purchasers or those who are in dialogue with customer service.

Klaviyo Meta integration pro tip: Read all the ways brands use the Klaviyo x Meta integration.

The results were clear

The US numbers told a compelling story:

For example, our Mermaid Garden print segment had 804 people, with 15 converters. The Moonflower print performed exceptionally well with 57 converters.

We essentially doubled our results while reaching 50,000 fewer people. The conversion rate difference was staggering.

What made this paid test work

3 key factors contributed to the success of this approach:

1. Audience quality over quantity

The Klaviyo audiences were incredibly specific. These weren’t just people who had visited our website or who had interacted with us on social. They were individuals who had actively requested to be notified when specific products came back in stock.

This level of intent made all the difference.

2. Consistent creative

We kept everything consistent except the audience. We used the same copy, same images, and same budget allocation. This allowed us to isolate the impact of audience targeting without variables skewing the results.

We used proven creative assets, like images and copy that had performed well when these products originally launched. This eliminated creative performance as a variable and made the audience effectiveness even more apparent.

Image source: Kulani Kinis

3. Timing

Interestingly, newer prints outperformed older ones, even when the older designs (like Mermaid Garden) had been extremely popular at launch. This suggests there’s a sweet spot for running these campaigns when interest is still fresh.

3 key learnings + applications

Product insights

The granular data revealed which prints resonated most with our audience. Moonflower’s strong performance told us something valuable about customer preferences that we could feed back to our design and production teams.

Scalability considerations

We started with a $100 daily budget per audience and scaled to $200 once we saw how well it performed. This suggests the approach can handle increased investment until you hit saturation.

Market differences

The US test significantly outperformed Europe, primarily due to audience size. Smaller segments (300 people vs. 3,000) didn’t provide enough data for Meta’s algorithm to optimize effectively.

Beyond back-in-stock: other applications

The Klaviyo x Meta integration opens up numerous possibilities:

• Exclude customers with open support tickets from seeing ads.
• Target RFM segments (including customers at risk of churning) who aren’t responding to email.
• Create lookalike audiences based on high-intent segments.
• Test different audience exclusions during major sale periods.

Ben Zettler, founder of Zettler Digital, recommends improving your conversion rate with Meta ads by building smarter Klaviyo segments.

“Use Marketing Analytics to create RFM segments based on recent, frequent, and high-value purchasers, then sync those audiences to Meta for precise personalization and effective exclusions,” he suggests. “Brands winning here are using Klaviyo to make sure every ad reaches the right people and avoids wasting budget on the wrong ones.”

3 implementation tips when using the Klaviyo Meta integration

If you’re looking to implement a similar test ahead of Black Friday Cyber Monday, consider these tips:

1. Start simple

Don’t try to segment every product immediately. Choose a few high-performing or high-interest items to test the concept.

2. Consider your business model

This approach works particularly well for brands that:

• Have products with longer lifecycles
• Generate meaningful back-in-stock demand
• Can create distinct customer segments based on behavior

It makes less sense for fast fashion brands with constantly changing inventory.

3. Prepare for BFCM early

This type of testing is ideal to run months before major sale periods. It gives you time to understand which audiences perform best and refine your approach before the high-stakes shopping seasons.

If you can hit the ground running, August is a great time to set a test like this up.

The bigger picture: omnichannel cohesion

The integration between Klaviyo and Meta represents a significant opportunity for brands to make their paid advertising more personal and effective. By using the intent data you’re already collecting, starting with a clear hypothesis, and maintaining strict testing controls, you can create audiences that perform dramatically better than traditional retargeting approaches—as long as you’re willing to scale what works.

In our case, that meant doubling down on hyper-targeted audiences that delivered twice the results at a lower cost per acquisition.

For brands looking to improve their paid media efficiency, this approach offers a clear path forward: use the customer data you already have to create more relevant, higher-converting advertising experiences.

Klaviyo is the only CRM built for B2C. When we use it to its full capacity, the results are unmatched.

“Klaviyo’s segmentation isn’t just for owned messaging,” Zettler emphasizes. “Sync those audiences into ad platforms for true omnichannel impact. When customers see consistent, relevant messaging everywhere, conversion and retention improve.”