Klaviyo and Mailchimp are the two platforms most Shopify merchants start with when they decide to take email seriously. They're also, increasingly, the two platforms most merchants switch between, in both directions, when their programme evolves beyond what they initially needed.
This is not a review. It's a framework for deciding which platform is right for a specific programme at a specific stage. Both platforms are capable and well-maintained. The difference is in what they're optimised for, and those optimisations matter enormously when you're trying to build a programme that compounds over time rather than one that just sends campaigns.
What each platform is actually optimised for
Mailchimp is optimised for accessibility and breadth. It's designed for teams with limited technical resources who need to get an email programme running quickly, without deep platform expertise. Its automation builder is visual and approachable. Its template library is extensive. Its pricing model (free tier, then volume-based) makes it accessible to brands in early stages.
Klaviyo is optimised for Shopify-native performance. Its data model is built around e-commerce events, viewed product, added to cart, purchased, refunded, in a way that Mailchimp's was not designed to handle natively. Its segmentation is more granular. Its reporting is more directly connected to revenue. Its flows are more configurable. It also costs more and requires more technical setup to get right.
The short version: if you're building a basic email programme and want to get started quickly, Mailchimp is fine. If you're building a programme where automated flows are core to your revenue model, Klaviyo is a significantly better tool.
The Shopify integration: a genuine difference
Klaviyo's Shopify integration is native, it's built into the Klaviyo product as a first-class feature, not a third-party connector. This means event data passes to Klaviyo in real time: when a customer views a product, adds to cart, completes a purchase, or triggers a refund, that event is available in Klaviyo within seconds. You can build triggers and segments directly against those events without middleware.
Mailchimp's Shopify integration was rebuilt after the two companies ended their official partnership in 2019. The current integration works, but it relies on a third-party connector (Mailchimp for Shopify, or similar apps on the Shopify App Store). The data passes reliably for the most common use cases, purchase confirmation, cart abandon, but event granularity and real-time sync lag behind what Klaviyo offers natively.
For a programme that relies heavily on browse-abandon, viewed-product triggers, or product-specific segmentation, this difference is significant. For a programme that primarily sends campaigns and a simple abandoned-cart flow, it's less likely to matter in practice.
Segmentation: where the gap is largest
Klaviyo's segmentation engine is its clearest competitive advantage. You can build segments against any combination of event data, purchase history, predicted lifetime value, engagement behaviour, and custom properties, all in a single interface, with live audience previews as you build.
Mailchimp's segmentation is functional but limited. The segment builder handles standard conditions (purchase frequency, tag-based groups, engagement behaviour) but doesn't have native support for more granular e-commerce logic like "customers who purchased from category X but never from category Y" or "customers whose predicted LTV places them in the top decile."
If your programme's revenue model depends on sophisticated segmentation, RFM tiers, category-specific targeting, predictive churn prevention, Klaviyo is the right tool. If your segmentation needs are simple, active vs lapsed, welcome series, promotional calendar, Mailchimp handles those cases without limitation.
Pricing: the honest comparison
Mailchimp's pricing is simpler: free up to 500 contacts (with Mailchimp branding on emails), then tiered by contact count. The Essentials plan starts at approximately £11/month for up to 500 contacts; the Standard plan (which includes automation and A/B testing) starts at approximately £17/month.
Klaviyo prices by active profile count. A "profile" is any contact who has received or can receive marketing, whether or not they're currently subscribed. This means your billing base in Klaviyo grows with your database, including unsubscribed contacts you've suppressed but haven't deleted. For a programme with a large suppressed list, this can produce unexpected billing increases. Budget for 30-40% more profiles in Klaviyo than you have active email subscribers.
At 5,000 active contacts, Klaviyo's Email plan is approximately £90/month; Mailchimp's Standard plan is approximately £60/month. At 50,000 active contacts, Klaviyo is approximately £450/month; Mailchimp Standard is approximately £260/month. At 200,000+ contacts, the pricing gap narrows as both platforms move to custom contracts.
The question isn't which is cheaper. It's whether Klaviyo's revenue performance advantage (which is real, but not guaranteed) justifies the price premium. For a high-AOV e-commerce brand with a large lapsed database and a sophisticated flow architecture, it almost always does. For a low-AOV brand with a small list and a simple programme, Mailchimp's lower price point is a rational choice.
Migration: when to switch and how to do it
The signal to switch from Mailchimp to Klaviyo is not "we've heard Klaviyo is better." It's "we've hit the ceiling of what Mailchimp's data model allows us to do." Specifically: if you're trying to build segments or triggers that Mailchimp's interface can't express, or if your abandoned-cart performance is being constrained by integration latency, those are the technical signals that justify a migration.
Migration is a two-week project minimum: export lists, map custom properties, rebuild flows (don't migrate, rebuild, with the opportunity to improve), rebuild templates, test triggers against Shopify events, and run both platforms in parallel for one sending cycle before cutting over fully. Don't cut over in peak trading periods. Rebuild, test, cut over in a quiet week.
The signal to stay on Mailchimp (or to reverse a Klaviyo migration) is simpler: if your team doesn't have the technical capacity to maintain Klaviyo's more complex data model, the platform's power is wasted. A simple programme run well on Mailchimp outperforms a complex programme run badly on Klaviyo. Tool selection is secondary to execution quality.