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Klaviyo and Customer.io are two of the most popular email marketing and automation platforms used by e-commerce brands and online businesses. Choosing the right platform is crucial for business owners who want to drive sales, nurture customer relationships, and create highly targeted marketing campaigns.

This article provides an in-depth comparison of Klaviyo vs Customer.io across several key criteria to help you determine which solution best fits your business’s needs.

We will evaluate categories like market position, ease of use, customization options, built-in features and functionality, performance metrics, quality of customer support, pricing models, overall reputation, and more. By the end, you’ll have a clear understanding of the pros and cons of each email marketing platform and be equipped to select the best one to achieve your e-commerce or digital marketing goals.

1. Understanding the Basics

Founded in 2012 by Andrew Bialecki and Ed Hallen, Klaviyo is a rapidly growing email marketing and automation platform built for e-commerce. With over 100,000 businesses using Klaviyo, they have established themselves as a market leader especially popular among small to midsize online retailers.

Some sources estimate $1.5+ billion in transactions powered by Klaviyo in 2021 alone. They have raised over $208 million in funding to date. While Klaviyo does not disclose exact user numbers, its customers include major brands like Chubbies Shorts, Drizly, and Huckberry.

Klaviyo has cultivated an active user community with a popular Facebook group called Klaviyo Pros focuses on email strategy and platform best practices. The group currently has over 2,000 members.

Launched in 2012 by Colin Nederkoorn, Customer.io is venture-backed marketing software aiming to personalize messaging at scale. Leaders like Pebble Watch, HelloFresh, and TheSkimm represent some of their 10,000+ customers.

While smaller in market share than Klaviyo, Customer.io has an impressive client roster and an estimated $1 billion in transactions driven annually. They have raised $75 million in funding as of 2020. Exact user numbers are not public.

Customer.io hosts an exclusive private Slack community that users can join as well as an active Facebook page with over 1,000 followers focused on marketing, email deliverability, and Customer.io best practices.

2. Features and Functionality



Klaviyo offers a robust suite of automation tools to help e-commerce brands customize flows and campaigns. You can create automated workflows triggered by actions like signing up for an email list, making a purchase, abandoning a cart, and more. These automations can send targeted emails, SMS messages, and push notifications, and can even update customer profiles or create custom segments.

Some standout Klaviyo automation features include behavioral targeting, ratings-based flows, and predictive models. You can automatically enroll customers’ inflows based on their on-site behaviors – like browsing certain product categories or reading particular blog posts.

Ratings-based flows let you ask for ratings or reviews and then trigger custom experiences for promoters, passives, or detractors. Predictive models use machine learning to determine each subscriber’s propensity to take actions like purchase or unsubscribe. This allows for highly personalized messaging tailored to individual subscriber needs.

Klaviyo also makes it simple to create multi-step automation with conditional logic and variables. You can iterate on your automation to optimize performance over time. Detailed analytics provide insight into which flows and campaigns drive the most revenue. Overall, Klaviyo sets itself apart with predictive segmentation capabilities and the ability to easily scale complex, personalized automation scenarios.


Customer.io enables both email and SMS automation triggered by events – from signing up for a newsletter to adding items to a cart to making repeat purchases over time. You can target customers based on properties and past behaviors or set up schedules to automatically enroll users in campaigns on a certain cadence.

Key automation features include segmentation by cohort and the ability to A/B test different flows. For example, you could target one promo email to new subscribers from the past week and then A/B test subject lines for the most engagement.

Another great feature is Customer.io’s native integration with many e-commerce platforms – allowing you to instantly access customer purchase data to trigger post-transactional automation.

While Customer.io doesn’t offer quite as advanced predictive modeling or machine learning capabilities as Klaviyo, it still provides robust tools for segmented, automated communications. You’ll be able to execute multi-channel campaigns tailored to the customer lifecycle stage and previous behaviors.

Overall, Customer.io strikes a balance between ease of use and sophisticated functionality when it comes to building automated email and SMS engagements.

Winner: Klaviyo

Klaviyo is the winner for best automation capabilities due to the predictive modeling and machine learning features that enable extremely customized, high-converting flows and campaigns. While Customer.io has great foundational automation with e-commerce integrations, Klaviyo has more advanced built-in segmentation and personalization capabilities.

Email Templates


Klaviyo offers hundreds of professionally designed, mobile-optimized email templates to choose from for your campaigns and automation. Templates are organized by goal – whether you want to drive sales, launch new products, create browse abandonment flows, or more.

Most templates are customizable, allowing you to tweak elements like images, colors, and text while preserving responsive layouts.

Standout features include full analytics per template to see open, clickthrough, and conversion rates to optimize underperforming templates. There is also an integrated Template Editor enabling easy drag-and-drop creation and editing without leaving Klaviyo. Dynamic Content Tags let you insert customer data like names, interests, or purchase information to personalize at scale.

Overall, exceptional visual email design capabilities coupled with dynamic personalization make it simple for users of any skill level to create polished, high-converting email templates with Klaviyo.


Customer.io also provides professionally designed templates for email campaigns, though their catalog seems less robust compared to Klaviyo’s offerings. Template categories range from welcome series to winbacks, referrals, subscriptions, and more.

The Template Editor enables drag-and-drop creation and editing of mobile-friendly layouts. You can upload images, customize colors/fonts, and leverage Customer.io’s liquid templating language to dynamically insert subscriber attribute info. Similar to Klaviyo’s analytics, you can view and compare open/click rates for each template.

While still solid, Customer.io templates have slightly less pizazz in terms of modern design than Klaviyo counterparts. Their template analytics seem less customizable as well – for example no data on email revenue influence or conversion performance. But core responsive email editing and creation abilities are on par.

Winner: Klaviyo

Klaviyo wins for best email templates thanks to an abundance of professionally designed, merchandising-oriented layouts coupled with robust template analytics. Customer.io provides all expected baseline email editing tools but falls slightly behind on both template design and analytics/optimization capabilities.



Klaviyo enables advanced subscriber segmentation with tools to divide your audience into highly targeted lists and groups. You can create segments based on any data points tracked – from email engagement metrics to on-site behaviors.

Klaviyo’s platform makes it easy to segment by transactional messages criteria ranging from simple demographics to granular metrics like cart abandonment rate or category affinity score.

Standout segmentation features include predictive filters, which use machine learning to group subscribers likely to exhibit behaviors like purchasing or churn risk, allowing for tailored messaging to these groups.

Smarter List Management lets you automatically remove inactive subscribers from certain flows to keep metrics like open rates high. Custom metrics empower granular segmentation – for example, segmenting by quiz scores, API data on purchase recency/frequency, and more.

Overall, Klaviyo gives exceptional flexibility to slice, dice, and automate your subscriber segments for personalized communications aimed at driving conversions.


Customer.io enables segmentation with cohorts, manual lists, and basic event-driven triggering capabilities. You can group subscribers using properties like demographics, purchase history, past campaign interactions, app usage data, and more.

The customer lifecycle stage is easy to define with tools to designate users as new, returning, active, inactive, or churned then message each group differently.

While core segmentation abilities are fairly robust, Customer.io lacks some of the advanced predictive modeling and machine learning smarts showcased in Klaviyo. Customer.io also does not include features like automated subscriber pruning from low-performing segments. You have access to rich data for manual segmentation, but less AI assistance for optimizing how groups are carved.

Winner: Klaviyo

Klaviyo wins best segmentation thanks to machine learning algorithms that drive predictive recommendations for ideal audience grouping coupled with automation to continually refine your high-value niche segments. Customer.io has wide data interoperability for insights-driven segmentation but trails slightly on AI-powered optimization.



Klaviyo shines when it comes to email and marketing analytics. Their platform enables deep analysis across customer segments and campaigns to quantify effectiveness. Flexible reporting dashboards let you examine metrics ranging from email deliverability to conversion impact to ROI across automations, flows, and templates.

Standout analytical features include multi-variant testing – the ability to instantly A/B test email subject lines, content, send times, formats, and more to optimize campaign performance. Custom metrics empower analyzing the influence of communications on business KPIs like average order value.

Klaviyo’s proprietary algorithm Score identifies your absolute best customers – quantifying individual subscriber value based on predictive models considering past and likely future value.

For data junkies, Klaviyo is a dream with granular analytics revealing both micro and macro performance insights from all marketing activities. This allows informed optimizations that tangibly improve critical metrics.


Customer.io also provides email analytics enabling you to report on deliverability, open rates, clickthroughs, conversions, and unsubscribe impact across campaigns. Dashboard views make it simple to compare the performance of various automation, journeys, and templates side-by-side for optimization.

Integrations with business intelligence tools like Mixpanel, Mode, and Looker extend analytical abilities.

Key features include A/B testing different subject lines and content to determine what resonates most with subscribers. Analytics are also segmented by various user properties and custom traits to quantify how campaigns perform among distinct audiences. This allows targeting underperforming segments with modified messaging as needed.

For most use cases, Customer.io supplies sufficiently robust analytics. However, data customization and segmentation capabilities do not seem on par with Klaviyo’s more granular offerings.

Winner: Klaviyo

Klaviyo wins the best analytics thanks to its deep segmentation abilities and comparative insight across email activities. Customer.io covers analytics basics well but cannot match the customization and predictive rigor of Klaviyo reporting. For quantifying email influence on revenue and customer lifetime value, Klaviyo is superior.

Unique Features


A few special features make Klaviyo stand out from other email platforms beyond robust analytics and automation. One is exemplary deliverability with proprietary handle mapping technology ensuring 99%+ inbox placement across Gmail, Outlook, Yahoo, and more. This protects email sender reputation which is essential for making it to the primary tab.

You can add apps for Klaviyo customer data which comes in handy for small teams engaging customers, and the platform also integrates directly with many popular e-commerce platforms like Shopify, Magento, and WooCommerce. This enables effortless data sharing, reducing work reconciling separate systems. Finally, Klaviyo offers SMS capabilities expanding campaign reach beyond email alone. Sophisticated automation couples these communication channels for highly targeted cross-channel nurturing.

Between industry-leading deliverability, deep e-commerce connections, and multi-channel messaging, Klaviyo checks all boxes as an espoused “hub” for online retail marketing technology stacks.


Distinct Customer.io strengths come via natively unified email and SMS coupled with proprietary predictive models that classify user likelihood to convert across customizable time ranges. So you can easily determine who will likely buy again in the next 7, 30, or 90+ days then target them appropriately.

Another neat feature is integration with the popular call tracking platform RingDNA, enabling call log data injections for incorporating into customer records, segments, and multichannel automation. This caters to communications to users’ channel preferences.

Finally, for dev-savvy users, Customer.io has robust event streaming and webhook abilities connecting disparate mobile and web apps to facilitate real-time data centralization for messaging personalization.

Winner: Tie

Both Klaviyo and Customer.io have unique strengths that make them well-suited to particular e-commerce use cases. Klaviyo optimizes the traditional email sphere with class-leading inbox deliverability, platform integrations, and multi-channel abilities.

Customer.io merges predictive intelligence with emerging channels via SMS and voice automation powered by streaming event architectures. Differentiating features accordingly appeal to varied audiences.

3. Ease of Use


Klaviyo prides itself on providing an intuitive user interface and easy onboarding even for email marketing beginners. The dashboard layout enables quick access to key functions like building workflows, creating campaigns, segmenting your list, and analyzing performance.

Drag-and-drop workflow builders, pre-designed templates, and customizable metrics make it simple to execute fairly sophisticated campaigns without extensive expertise.

The platform prioritizes speed – loading pages, assets, and data visualizations rapidly so users spend time acting on insights rather than waiting on them. Klaviyo also offers thorough support documentation plus tutorial videos for grasping core capabilities or trickier activities like custom CSS.

While power users will appreciate the scale of flexible tools, new email marketers can still get up and running quickly thanks to intuitive navigation and guidance.


Customer.io tries to strike a balance between simplicity and sophisticated functionality, though has historically targeted more technical users compared to Klaviyo. Recent redesigns have improved usability for less experienced email marketers via tidy dashboard arrangements that spotlight key campaign creation/reporting abilities.

You still may need some baseline comfort with code due to Customer.io’s liquid templating syntax required for personalization.

The Android mobile and drag-and-drop workflow/nurture builders enable accessible automation construction without extensive technical expertise. This means you don’t have to be a pro to provide world-class customer experiences.

However, some areas like building custom metrics require coding proficiency for complex rule creation and data manipulation. This could be a deal-breaker for small businesses but larger corporations will appreciate having greater control. Documentation is fairly robust to support self-guided learning for newer users. However, the platform lacks tutorial videos which Klaviyo offers.

Winner: Klaviyo

Klaviyo wins the best ease of use, thanks to purposeful UI/UX design enabling intuitive navigation plus integrated educational assets optimizing onboarding. Customer.io caters better to technical users but recent updates improve new user accessibility. Still, Klaviyo pips them for rapid campaign execution requiring less specialized knowledge.

4. Email Deliverability


Klaviyo rightfully touts exceptional email deliverability thanks to proprietary innovations ensuring inbox placement across major ISPs. Their patented Relevance Engine facilitates customizable sender scoring so that recipient ISPs recognize your mail’s value – leading to primary inbox delivery rather than spam or promotion tabs.

Klaviyo also enacted the innovative Metric System gaining trust with Gmail by sharing selected metrics on audience engagement. This grants preferential treatment in Gmail routing. Further, Klaviyo’s Handle Mapping ensures accurate recipient profile matching between senders and receivers – reducing spam red flags that lessen deliverability.

Thanks to these advances, Klaviyo clients enjoy 99%+ inbox placement and exceed industry benchmarks for open and clickthrough rates across email campaigns sent through the platform. At scale, companies can send messages and be confident that their email and in-app messages will reach the audience’s eyeballs.


Customer.io adopts standard best practices for maximizing email deliverability, advising clients on sender reputation, content personalization, list hygiene, and other proven tactics that enhance trust and inbox placement with ISPs.

They provide deliverability monitoring tools highlighting potential red flags that could trigger spam filtering. Reports also benchmark open/click rates against your industry averages. For inbox placement optimization, Customer.io relies more on general community standards enforcement rather than specialized proprietary deliverability inventions like Klaviyo created.

The company promises inbox rates exceeding 90%, which is quite positive but still trails the Klaviyo gold standard. Deliverability fundamentals seem covered but lack innovative developments.

Winner: Klaviyo

Klaviyo is the clear inbox deliverability winner thanks to multiple proprietary innovations like Relevance Engine and Metric System which enhance trust with major ISPs. This leads to improved messaging outcomes. Customer.io delivers on email fundamentals but cannot match Klaviyo’s industry-leading sender reputation and 99%+ inbox placement rates.

5. Customer Support and Community


Klaviyo provides email support, chat support, and phone customer support with US-based representatives available 24/7. They also offer exceptional community resources including a public help documentation portal with hundreds of searchable articles plus video tutorials covering core platform capabilities and tips for email marketers.

As mentioned in Section 1, Klaviyo has an active Facebook Group called Klaviyo Pros with over 2k members focused on email and automation best practices where community experts and Klaviyo staff share insights.

This facilitates troubleshooting, idea exchange, and camaraderie. Klaviyo also hosts free instructional Masterclass webcasts educating on using email and SMS to acquire, retain, and engage customers.

Between always-available support channels, thorough help documentation, instructional videos, a vibrant community forum, and regular educational programming, Klaviyo customers have exceptional assistance resources to optimize effective platform usage.


Customer.io offers business-hour email support along with chat functionality right within the platform interface for real-time troubleshooting. Their public support site includes hundreds of help articles covering core platform applications, common use cases/questions, plus developer documentation for coding custom solutions.

While they lack Klaviyo’s expansive video tutorials, the written content is thorough. As referenced earlier, Customer.io facilitates a private Slack user community for idea exchange and troubleshooting as well as a 1,000-member strong Alumni Facebook Group. So ad-hoc community assistance aligns well. They also regularly host free educational and networking events for current users and alumni.

Winner: Klaviyo

Klaviyo wins best community and support thanks to 24/7 live channels supplemented by on-demand video tutorials, a vibrant public online forum, and regular educational programming for continued learning. Customer.io hits community and self-service benchmarks but phone support availability only during business hours is less accommodating.

6. Integrations


Klaviyo connects with hundreds of platforms spanning crucial online business capabilities – from e-commerce stores to CRM databases, marketing analytics tools, live chat systems, and more for additional workspaces.

Native integration with e-commerce leaders like Shopify, BigCommerce, Magento, and WooCommerce facilitates effortless list building plus access to detailed order data for segmentation and personalization. CRM syncing with HubSpot, Salesforce, and others enables consolidated tracking of subscriber activity across business systems.

Klaviyo also offers a custom API plus Zapier and Workato compatibility empowering connections with niche apps that may not be covered through native integration. This makes it ideal for high-growth companies.

This flexibility allows comprehensive centralization of data sources into Klaviyo profiles available for targeted messaging alignment across acquisition, retention, and re-engagement campaigns.


Customer.io delivers native integration with major e-commerce platforms like Shopify and Magento that imports key transactional data powering segmentation and automation processes. CRM data unification is enabled through customers’ Salesforce environment syncing contact, deal, and activity information that can personalize communications.

For less common connections, Customer.io does facilitate custom API development access. Like its competitor, Customer.io lets you have two workspaces or more. However, they presently lack packaged Zapier/Workato compatibility that eases ad-hoc linking as we see with Klaviyo.

But between key unified commerce, CRM, and custom logic abilities – the core abilities to centralize data for segmentation and targeting at scale is achieved. Gaps seemingly exist though among less popular platform utilities.

Winner: Klaviyo

Klaviyo wins best platform integrations thanks to the breadth of native connectivity spanning e-commerce tools, CRMs, analytics, live chat, and more – coupled with Zapier/Workato services enabling broad custom use case platform connections that Customer.io currently falls short on.

7. Klaviyo vs Customer.io Pricing


Klaviyo offers flexible, scalable pricing plans based on the number of contacts, email volume sent monthly, and other add-ons. Their Free plan supports up to 500 contacts and 125,000 emails per month – a generous allotment suitable for early-stage e-commerce brands.

Paid tiers scale up substantially supporting millions of contacts and email volumes in the billions annually. Exact pricing is custom-quoted based on projected usage. Features align across plans with higher tiers focused on enabling capacity rather than functionality limits. Klaviyo also offers discounted rates for annual contracts and subtracted rates for customers providing their IP addresses.

Overall, transparent volume-based pricing provides strong alignment and value predictability punctuated by an impressively full-featured free tier to support young businesses before needing to upgrade.


Customer.io pricing follows a tiered model based on the number of contacts with volume discounts at higher levels. Plans start at $100 per month for 5,000 contacts and 1 million emails sent per month.

The Premium plan costs $1,000/month for a custom profile and email volume. Enterprise quotas for 250,000+ contacts are available via custom quote

Overall, Customer.io packs strong capabilities per priced tier but lacks a free introductory plan that Klaviyo provides for early-stage needs. Enterprise quotas also seem costlier.

Winner: Klaviyo

Klaviyo wins the best pricing thanks to a free 500-contact plan, transparent volume-based quoting, and various cost-control discounts. Customer.io packs features per tier but starts paid-only and lacks foreseeable cost scaling. Klaviyo’s free inclusion for startups provides better onboarding value.

8. Reviews and Reputation


Klaviyo earns strong reviews across evaluation platforms like G2Crowd, Capterra, and Software Advice highlighted by ease of use, automation features, and quality support. They average around 4.5 out of 5 stars.

Positive feedback centers on the intuitive drag-and-drop interface enabling accessible campaign creation for all user skill levels. Reviewers also praise rich integration capabilities, excellent deliverability, migration support, and top-notch customer service response times.

Less favorable notes include occasional UI latency when loading detailed analytics plus steep learning curves to master advanced functionality.

With 95% of users on Capterra saying they’d recommend Klaviyo and the platform sporting a shining 4.7/5 average across sites, the email marketing leader continues demonstrating product excellence and customer satisfaction.

See Klaviyo’s reviews on G2, Capterra, and TrustRadius.


Customer.io earns solid market appraisals as a leading SMS/email solution earning around 4 out of 5 stars across evaluation sites. Users highlight granular analytics, segmentation capabilities, and predictive modeling as key strengths. Less favored features include the comparatively steeper learning curve along with the inability to tag historical campaign data.

Reviewers on sites like G2 and Capterra particularly praise Customer.io’s templating language flexibility empowering advanced personalization with code rather than just drag-and-drop tools. However, some critique that same complexity as overkill for users with low technical proficiency. Integrations, deliverability, and support responsiveness garner strong marks as well.

Winner: Klaviyo

Klaviyo wins best reviews/reputation by quantitatively averaging higher satisfaction rates emphasizing ease of use and support – with 95% of Capterra reviewers likely to recommend the platform. Customer.io trails closely behind with strong evaluations as well among technical users. But comparatively steeper learning curves cost marginal points.

9. Customer.io vs Klaviyo: FAQ’s

Klaviyo FAQs

  • What types of email campaigns can I create with Klaviyo?

    You can create all types of email campaigns from welcome flows to cart abandonment series to promotional blasts. Pre-designed templates help execute common campaigns quickly.
  • Does Klaviyo have drag-and-drop workflow builders?

    Yes, Klaviyo enables building automated email workflows via an intuitive drag-and-drop interface without needing to code.
  • Can Klaviyo track SMS campaigns too?

    Yes, Klaviyo supports targeted SMS messaging in addition to email. Sophisticated SMS workflows are possible.
  • Is Klaviyo designed for e-commerce companies?

    Klaviyo specializes in the e-commerce sphere with deep integrations to major platforms like Shopify and Magento empowering personalized, targeted email and SMS.

Customer.io FAQs

  • Does Customer.io offer free trials for new users?

    Yes, Customer.io provides 14-day free trials including 10,000 free emails along with full platform access to evaluate capabilities.
  • What types of metrics can I track with Customer.io?

    You can track comprehensive email engagement metrics like opens, clicks, conversions, etc. plus custom event data all segmented with filtering and comparatives.
  • Does Customer.io allow sending SMS campaigns?

    Yes, Customer.io enables sending triggered SMS messages in addition to email campaigns all from an integrated platform.
  • Is Customer.io just for email marketing?

    No, Customer.io specializes in full lifecycle marketing across email, SMS, push notifications, and more to engage users on preferred channels.

Final Thoughts

Choose Klaviyo if…

Klaviyo is an ideal choice for e-commerce brands wanting to accelerate growth through targeted, automated email and SMS marketing campaigns. Thanks to advanced segmentation capabilities, highly customizable flows and templates, and deep e-commerce platform integrations – Klaviyo empowers merchants to easily nurture customer relationships driving loyalty and conversions.

With class-leading deliverability maximizing inbox placement, flexible pricing plans including a free tier for early-stage needs, and best-in-class performance across ease of use, features, and support satisfaction – Klaviyo enables both new and established direct-to-consumer retailers to skillfully move beyond basic email blasts to executed sophisticated omnichannel strategies with tracking to quantify each effort’s revenue influence.

You may also be interested in reading about Klaviyo alternatives for a better idea of which email marketing platform may be the best for you.

Choose Customer.io if…

Customer.io suits online businesses seeking an enterprise-grade solution unifying real-time user data across engagement channels including email, SMS, mobile push notifications, and more – facilitated by event streaming integration capabilities.

Sophisticated segmentation by cohorts, behavioral modeling, and partial user profiles support life cycle marketing automation even in cases with extensive anonymous site activity before conversion. Customer.io also provides accessible yet versatile tools to front-line product, engineering, and marketing staff to collaborate in executing well-targeted campaigns.

For other fast-scaling e-commerce brands, the Customer.io blend of segmentation finesse, technical flexibility, and unified visibility across channels positions the platform as a long-term solution worthy of growing into rather than outgrowing over time.

Choosing the right email and customer engagement platform is crucial for delivering value across both customer experience and business performance metrics. We urge you to thoroughly assess your use case, technical requirements, and functionality needs against the pros/cons of solutions like Klaviyo and Customer.io showcased here.

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