If your revenue comes from orders in a store, use Klaviyo: the commerce sync, per-flow revenue attribution, and predictive metrics are not matched by anything else. If your revenue comes from subscriptions driven by what people do inside a product, use Customer.io: it triggers on real product events and adds in-app messaging that Klaviyo does not have. The rest is detail, and both products have a billing model you should understand before you sign anything.
The vertical split is real, not marketing.
Klaviyo is the ecommerce and retail leader, and its data model shows it. Everything assumes a store: orders, products, carts, browse sessions, and revenue attached to the flow that produced it. Deep Shopify sync is the flagship integration, and the predictive layer, customer lifetime value and churn likelihood, is trained on purchase behavior. If you have a catalogue and a checkout, this is a product designed around your business.
Customer.io is a customer messaging platform built around real-time event-triggered journeys for software products. It expects you to pipe in product events and custom attributes, then gives you a multi-branch visual builder, segmentation on behavioral plus custom attributes, A/B testing inside a journey, and email, SMS, push, in-app, and webhook steps in the same flow. There is no catalogue concept because it does not assume you sell things.
Two kinds of reader end up comparing them anyway. Shopify brands questioning what Klaviyo now costs, and SaaS teams who only know Klaviyo because an ecommerce friend recommended it. The answers for those two readers are different, so the sections below are split along that line.
Two readers, two different answers.
You run a store and the Klaviyo bill keeps climbing.
Customer.io is almost certainly not your escape route. It has no commerce data model, no catalogue, and no revenue attribution per flow, so you would be trading the thing you are paying Klaviyo for in order to fix a billing complaint. The cheaper fix is usually profile hygiene: work out how many of your active profiles are people you will genuinely message again, suppress or delete the rest, and re-run the numbers. Teams routinely find a third of the bill is profiles that have not opened anything in two years. If after that the price is still wrong for your margins, you are looking for a different ecommerce platform, not for a SaaS messaging tool.
You run a SaaS product and someone told you to use Klaviyo.
That recommendation almost always comes from an ecommerce context, and it does not transfer. You will spend your first week bending product events into a schema built for orders, you will get no in-app channel, and the predictive metrics that justify the price are trained on purchase behavior you do not have. Customer.io, or a smaller tool built on product events, is the right shape. The one honest exception is a SaaS business with a real transactional storefront attached, where Klaviyo can still earn its place on the commerce side.
Customer.io and Klaviyo side by side.
| Dimension | Customer.io (mid-2026) | Klaviyo (mid-2026) |
|---|---|---|
| Built for | SaaS and product-event messaging. | Ecommerce and retail, Shopify above all. |
| Data it assumes | Product events and custom attributes you pipe in. | Store data through deep native commerce sync. |
| Channels | Email, SMS, push, in-app, webhooks. | Email, SMS, push. No in-app messaging. |
| Reporting | Thin relative to the journey builder. | Revenue per flow, predictive lifetime value and churn. |
| Entry cost | $100 a month floor on Essentials. | Free to 250 profiles, around $20 a month at 500. |
| Billing driver | Profiles stored plus email volume. | Active profiles: anyone emailable, textable, or push-able. |
| AI in 2026 | LLM Actions run a prompt on live customer data mid-workflow. | Marketing Agent drafts and assembles campaigns. |
Both billing models have a gotcha. Learn both.
Klaviyo's is the more notorious. In February 2025 it moved to billing on active profiles, which counts anyone who is emailable, textable, or push-able rather than only the people you actually contact. Users call it a success tax, because list growth raises the bill even when send volume is flat, and the backlash pushed Klaviyo's Trustpilot rating down to roughly 1.8. Read those reviews carefully: they are overwhelmingly about billing, not about whether the product works. The product is still very good at what it does.
As reported mid-2026, Klaviyo is free to 250 profiles, around $20 a month at 500 profiles, around $100 at 5,000, and around $400 at 25,000, with SMS added from around $15 a month plus message credits. There is no self-serve annual discount, so the usual lever for cutting 15 to 20 percent off a SaaS bill is not available to you.
Customer.io's gotcha is quieter but the same species. It bills on profiles stored plus email volume, and dormant profiles count. Essentials starts at $100 a month as of mid-2026, per Customer.io's pricing page, covering roughly 5,000 to 8,000 profiles and up to a million emails a month, with Premium from $1,000. Teams that import every user they have ever had and never prune are the ones who write the surprised invoice threads. Customer.io does run a startup program offering up to 12 months free for companies that have raised under $10 million, which is the single largest discount available on either platform.
The defense on both sides is identical and boring: decide what an active profile means for your business, suppress or delete the rest on a schedule, and review the count monthly rather than at renewal.
Channels: the in-app gap and the SMS overlap.
Both send email, SMS, and push. Customer.io adds in-app messaging and webhooks in the same journey; Klaviyo has no in-app channel. For an ecommerce brand that hardly matters, because the customer is not logged into an app most of the time. For a SaaS product it matters a lot: in-app is the only channel that reaches someone in the exact place the desired action happens, and it works for the large fraction of users who never open email.
Webhooks are the other quiet difference. Customer.io treating a webhook as a journey step means a lifecycle flow can update your own systems, notify Slack, or hand off to a sales tool as part of the same sequence. That is a software-company assumption baked into the product.
Attribution and AI: what each one leads with.
Klaviyo's reporting is its second-best argument after the Shopify sync. Revenue attributed per flow and per campaign, plus predictive lifetime value and churn likelihood, means the tool answers the question a store owner actually asks: which of these emails made money. Customer.io does not try to answer that, and its reporting is consistently described as thin relative to how strong the journey builder is, which is why teams usually run a separate analytics tool beside it.
On AI, both shipped something real in 2026 and they aimed at different jobs. Klaviyo's Marketing Agent drafts and assembles campaigns, and for teams that have adopted it, it now produces more than half of their campaigns. Customer.io's LLM Actions run an AI prompt against live customer data in the middle of a workflow, which is a builder feature rather than a content feature. Klaviyo is automating the writing; Customer.io is automating a decision inside the flow.
Which one to pick.
Pick Klaviyo if you sell physical or catalogued products, especially on Shopify, and you need to know which flow generated which revenue. Budget for active-profile billing, prune aggressively, and do not expect a self-serve annual discount. If the 2025 billing change is what brought you here, the round-up of Klaviyo alternatives covers where brands are actually moving, and the GetFluxly and Klaviyo comparison covers the SaaS-side mismatch specifically.
Pick Customer.io if your triggers are product events, your journeys branch, you want in-app messaging, and you have the engineering capacity to feed it data. Check the startup program first. If the $100 floor is the blocker rather than the product, the Customer.io alternatives page is the more useful next read.
Customer.io versus Klaviyo, common questions answered.
Is Klaviyo good for SaaS?
It is usable but it is not built for it, and the mismatch shows up in the data model. Klaviyo is organized around store data: orders, products, carts, and revenue per flow, with deep Shopify sync as its centre of gravity. A SaaS product has no orders to sync, so you end up pushing custom events into a schema that expects purchases, and you get no in-app messaging at all. If your revenue is subscriptions driven by in-product behavior, Customer.io is the closer fit.
Why is Klaviyo so expensive?
Mostly because of how it counts what you pay for. Since February 2025 Klaviyo bills on active profiles, meaning anyone who is emailable, textable, or push-able rather than only the people you actually message, and that change is the single biggest driver of complaints about the platform. Growth compounds it: as reported for mid-2026, email pricing runs around $20 a month at 500 profiles, around $100 at 5,000, and around $400 at 25,000, with SMS added on top from around $15 a month plus credits. There is also no self-serve annual discount, so there is no easy lever to pull.
What changed in Klaviyo's billing in 2025?
In February 2025 Klaviyo moved to billing on active profiles: any profile that can receive email, SMS, or push counts toward your plan, not just the ones you send to. Users describe it as a success tax, because a growing list raises the bill even if send volume is flat. The reaction was severe enough that Klaviyo's Trustpilot rating fell to roughly 1.8, driven by billing rather than product complaints. The practical defense is profile hygiene: suppress or delete profiles you will never message.
Which is cheaper to start, Customer.io or Klaviyo?
Klaviyo, clearly, at small scale. Klaviyo is free up to 250 profiles and around $20 a month at 500 profiles as reported mid-2026, while Customer.io starts at a $100 a month floor on Essentials per Customer.io's pricing page. The two converge around the 5,000 profile mark, where Klaviyo email runs about $100 a month and Customer.io's Essentials plan covers roughly 5,000 to 8,000 profiles for the same $100. Above that, both scale on profile counts, so the deciding factor becomes fit rather than price.
Does Klaviyo have in-app messaging?
No. Klaviyo covers email, SMS, and push, but it has no in-app messaging channel. Customer.io does, alongside email, SMS, push, and webhooks in the same journey. For a SaaS product this matters more than it sounds, because in-app is the only channel that reaches a user in the exact place the action you want them to take actually happens, and it reaches people who never open email.
Which has better reporting?
Klaviyo, and it is not close for revenue questions. Klaviyo attributes revenue per flow and per campaign out of the box and adds predictive metrics such as customer lifetime value and churn likelihood, which is why ecommerce teams tolerate the pricing. Customer.io's reporting is repeatedly described as thin relative to the strength of its journey builder, so teams that need deep analysis usually pair it with a separate product analytics tool.
Where does GetFluxly fit alongside Customer.io and Klaviyo?
GetFluxly is for SaaS teams that want product analytics and lifecycle email in one tool at a predictable price, rather than buying a messaging platform and an analytics platform separately. It tracks product events, builds the customer profile from them, runs segmentation and automations off that behavior, and sends through your own ESP, on one $29 a month plan priced by profiles tracked. If you run an ecommerce store on Shopify and need per-flow revenue attribution, use Klaviyo; nothing else matches it there. If you need branching multi-channel journeys at enterprise scale, use Customer.io.
Where GetFluxly fits, honestly.
Neither of these two solves the problem a small SaaS team usually has, which is that lifecycle email and product analytics live in different tools that disagree about who a user is. GetFluxly puts both in one place: product events feed the customer profile, the profile drives segmentation and automations, and the same events power funnels and retention reporting. One plan at $29 a month, priced by the profiles you track, and you keep your own sender.
Say plainly who should not pick it. Ecommerce brands should use Klaviyo; the commerce sync and per-flow revenue attribution are genuinely better than what we do, and no amount of positioning changes that. Enterprise teams running branching multi-channel journeys with in-app messaging at scale should use Customer.io and budget for it. GetFluxly is for the SaaS team between those two, the one that would otherwise be paying a $100 floor for a journey builder it half uses, plus a separate analytics tool to find out whether any of it worked.