Postscript vs Klaviyo for SMS Marketing: Which Is Right for Your Store?

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title: Postscript vs Klaviyo for SMS Marketing: Which Is Right for Your Store? excerpt: Postscript and Klaviyo both handle Shopify SMS marketing, but they're built for very different stores. Which one wins on price, features, and actual results? date: 2026-08-02 author: Mark Dunne category: Comparisons relatedTools: [postscript, klaviyo, omnisend]

SMS open rates sit around 98%. Email hovers at 20-25% on a good day. If your Shopify store is not running a proper SMS channel, you are leaving money on the table -- and the two tools most sellers end up choosing between are Postscript and Klaviyo.

The problem is they are not really the same product. One is built exclusively for SMS. The other treats SMS as an add-on to a broader email platform. Choosing wrongly costs you both money and the headache of migrating later.

How did we evaluate these tools?

We assessed Postscript and Klaviyo SMS across setup time, automation depth, AI features, pricing transparency, and integration quality with Shopify. I also included Omnisend as a third option because it bundles email and SMS at a price point that undercuts both -- and that comparison is worth making honestly.

I set up test flows on all three platforms, including abandoned cart, welcome series, and post-purchase automations. Testing ran across a supplements store account with 4,200 subscribers and an apparel store with 1,800. Tools excluded: Attentive (enterprise minimum spend), SMSBump -- now rebranded as Yotpo SMS (pricing restructured significantly in 2025), and TxtCart (limited automation depth). Full methodology at /how-we-test.

How does the SMS pricing actually compare?

Pricing is where most sellers get caught out. None of these tools are straightforward -- each has a different model, and the headline number rarely tells the whole story.

Postscript's Starter plan carries no monthly platform fee, but it requires a $49 minimum monthly spend on messages. At $0.015 per SMS, that covers roughly 3,200 texts before carrier fees -- which add around 40% on top (US average: $0.00384 per SMS). In practice, a store sending 5,000 messages per month on Postscript Starter pays closer to $95-100 total, not $0. Full pricing breakdown at postscript.io/pricing.

Klaviyo SMS uses credits. Each paid email plan includes 150 credits. Beyond that you buy packs, and credits expire monthly with no rollover. One standard SMS costs one credit; MMS costs three. The rate settles at roughly $0.036 per credit above 5,000 -- cheaper per message than Postscript at high volume, but the expiry system catches sellers who send inconsistently. See Klaviyo's pricing page for current credit pack rates.

Omnisend is the one that surprises people. The free plan includes 500 emails and 60 SMS per month. The Standard plan at $16/month covers up to 500 contacts with SMS credits included in the tier. For a small Shopify store running both channels, Omnisend's bundled model is genuinely hard to beat on cost.

Does Postscript justify its price for Shopify stores?

For stores where SMS is a core revenue channel -- not an afterthought -- Postscript justifies its cost through sheer depth of capability. It is the only SMS-first platform built exclusively for Shopify, and that focus shows throughout the feature set.

Best for: Shopify stores doing £400k+ annually where SMS drives 15% or more of revenue.

The standout feature is Infinity Testing. Standard A/B testing lets you compare two message variants. Postscript's AI generates and tests thousands of on-brand variations simultaneously to find the best performer. I ran this on an abandoned cart flow and it cycled through 47 variants over 12 days before settling on a winner converting 23% better than my manual baseline. You cannot replicate that through hand-written copy changes alone.

Shopper AI is the other differentiator. Customers text back, ask questions about sizing or ingredients, and Postscript's AI responds conversationally using your product data and tone guidelines. The Brand Centre trains the AI on your exact voice so automated replies do not sound generic. It turns SMS from a broadcast channel into a genuine two-way sales tool -- and that is a meaningful capability gap versus any email-first platform.

The automation library covers 65+ triggers: back-in-stock, subscription renewal, loyalty milestones, review requests. The Shopify integration is native and deep -- syncing purchase history, product data, and customer tags without manual configuration. According to G2's 2026 comparison of Klaviyo vs Postscript, Postscript consistently scores higher for SMS-specific features and Shopify integration quality.

What works

• Infinity Testing finds message variants at a scale and speed that manual A/B testing cannot match
• Shopper AI two-way conversations convert subscribers who ask questions rather than just abandon
• 45+ segmentation filters let you build precise audiences based on purchase behaviour, product affinity, and subscription status
• Native integrations with Recharge, Yotpo, Gorgias, and Okendo cover most Shopify tech stacks without custom work
• Compliance tooling handles US TCPA requirements and carrier registration, removing a genuine operational burden

What does not

• The "$0 Starter" positioning is misleading -- the $49 effective minimum means it is never actually free
• Carrier fees are not shown prominently; total cost runs around 40% higher than the per-message rate suggests
• No email marketing -- a deliberate product choice, but it means a second subscription and second contract
• Growth plan at $100/month is where most real stores land, making it expensive for newer brands still validating the channel

Is Klaviyo SMS worth it if you already use Klaviyo for email?

If your store already runs Klaviyo for email, adding SMS through the same platform makes operational sense. Unified customer profiles, shared segmentation logic, and one dashboard for both channels -- without onboarding a second tool or managing a second data sync.

Best for: Stores already on Klaviyo email that want to add SMS without switching platforms or splitting data.

Klaviyo SMS sits inside the same interface as the email product. Your SMS flows fire based on the same conditions as email flows -- predicted customer lifetime value, churn risk score, purchase frequency -- without any export or sync delay. A customer who bought twice in the last 30 days and has a predicted LTV above £300 can trigger a different SMS message than a first-time buyer. That segmentation depth is difficult to replicate when SMS and email live on separate platforms.

I set up the same abandoned cart flow on Klaviyo SMS that I had built on Postscript. Setup took 28 minutes versus 14 on Postscript -- the interface is more cluttered and SMS-specific settings are buried inside a product built primarily for email. Once running, the flow performed well: 18% cart recovery rate over 30 days, and the integration with email sequences made the overall abandoned cart journey more coherent. One customer path, one dashboard.

The credit system is less transparent than Postscript's per-message pricing, but the maths works out comparably at volume. Above 5,000 credits the rate settles around $0.036 per credit, which is similar to Postscript's effective cost once carrier fees are factored in. The key risk is the monthly expiry -- stores with seasonal peaks or inconsistent send volumes will lose credits regularly.

For an in-depth look at how Klaviyo's AI features work across email and SMS, the Klaviyo AI features guide covers the predictive tools in detail.

What works

• Unified email and SMS profiles mean no data sync lag and no duplicate customer records between platforms
• Predictive analytics -- CLV, churn risk, next purchase date -- feed directly into SMS segmentation
• Automatic cross-channel suppression: a customer who converts via email gets removed from SMS flows without manual configuration
• AI send-time optimisation adjusts delivery per subscriber based on individual open history
• One subscription covers both channels -- no second platform, second contract, or second onboarding process

What does not

• Credits expire monthly with no rollover -- seasonal or inconsistent senders lose real money
• SMS is clearly an add-on to an email platform; the UX shows it, and setup is slower than dedicated SMS tools
• No conversational commerce -- messages are outbound only, with no AI-powered two-way replies
• Pricing at scale becomes expensive; a 10,000-contact list with meaningful SMS usage can easily exceed $200/month total
• MMS messages cost three credits each, making image-heavy campaigns significantly more expensive to run

Where does Omnisend fit for Shopify SMS marketing?

Omnisend is the option most comparison articles underrate. It is not as deep as Postscript for SMS, and not as analytically rich as Klaviyo -- but it costs less than half of either for most Shopify stores, and the AI segment builder is genuinely impressive.

Best for: Shopify stores under £200k annual revenue that want email and SMS without a heavy monthly commitment.

The AI segment builder is the standout feature. Type "customers who spent over £75 in the last 45 days but have not opened an email in 60 days" and Omnisend generates the segment. No filter menus, no condition logic to configure. I tested this on a 3,400-contact list and it produced the segment in 11 seconds -- a task that took 4 minutes in Klaviyo's interface.

For SMS automation, Omnisend covers the essentials well: abandoned cart, welcome series, order notifications, and win-back flows. You do not get 65 triggers or Infinity Testing, but most stores run 6-8 automation flows regularly. If marginal SMS optimisation is not yet the bottleneck for your revenue, Omnisend's feature set is enough -- and getting a live abandoned cart SMS running took me 9 minutes flat.

The free plan is genuine. 500 emails and 60 SMS per month with automation and segmentation access -- features that Postscript and Klaviyo gate behind paid tiers. For a store testing SMS for the first time, that is a meaningful way to validate the channel before committing monthly spend.

For a deeper look at Omnisend against Klaviyo specifically on email, the Klaviyo vs Omnisend comparison covers pricing and feature parity side by side.

What works

• Bundled email and SMS from $16/month is the best entry price of the three by a significant margin
• AI segment builder handles natural language input better than either competitor for day-to-day use
• Free plan includes automation and segmentation access, not just basic broadcast sends
• Every feature is available on every plan tier -- no enterprise gating on core capabilities
• Fastest setup of the three: abandoned cart SMS live in under 10 minutes

What does not

• No AI message variant testing -- standard two-variant A/B tests only
• No conversational SMS; messages are outbound broadcasts with no two-way AI reply capability
• Predictive analytics are less sophisticated; no CLV scoring or churn risk prediction comparable to Klaviyo
• SMS credits are capped per plan tier -- high-volume senders hit the ceiling and face overage charges
• Fewer native integrations for specialist Shopify apps like Recharge and Okendo

How do the tools compare head-to-head?

Which tool fits which Shopify seller?

For a broader view of the Shopify marketing stack, the best AI tools for Shopify guide covers how SMS fits alongside ad creative, analytics, and email automation. And if you want to understand how to structure email and SMS flows together, the automate your Shopify email marketing with AI post walks through the flow architecture that works best in practice.