Klaviyo + Postscript Integration Guide (2026)

Most DTC brands eventually hit the same fork in the road: they run email on Klaviyo, love it, and then have to decide where SMS lives. Klaviyo has a perfectly capable native SMS product. Postscript is a Shopify-only SMS specialist that a lot of high-volume brands swear by. So the real question isn't "Klaviyo or Postscript" — it's whether running both actually makes sense, and if so, how to wire them together so they don't step on each other.

This guide covers exactly how the Klaviyo–Postscript integration works in 2026, how to set it up without breaking attribution, what it really costs, and how to decide whether you should consolidate on Klaviyo SMS or keep Postscript as a dedicated SMS engine.

Table of Contents

• The short answer
• What each tool actually does
• How the integration works
• Step-by-step setup
• Attribution: the part everyone gets wrong
• What it costs in 2026
• When to keep both vs. consolidate
• Common mistakes
• FAQ
• Getting help

The short answer

• Klaviyo does email + SMS + push in one platform. One customer profile, one segmentation engine, one flow builder for every channel.
• Postscript does SMS only, and only for Shopify. It's built by people obsessed with US SMS deliverability, carrier relationships, and conversational commerce.
• The integration is a one-directional data bridge, not a two-way merge. Postscript pulls Klaviyo/Shopify events so its SMS flows can trigger off the same behavior your email flows use.
• Run both if SMS is a serious, high-volume revenue channel and you want Postscript's deeper SMS tooling. Consolidate on Klaviyo if you want one profile, one attribution model, and simpler ops.

If you're not sure which side of that line you're on, you probably belong on Klaviyo SMS. The bar for justifying a second tool is higher than most brands think.

What each tool actually does

Klaviyo

Klaviyo is a full B2C marketing platform. Email, SMS, push, and now WhatsApp all live on the same customer profile. The advantages are structural:

• One profile, one source of truth. Every open, click, order, and text lives on the same record. Segmentation works identically across channels.
• Cross-channel flows. You can build a welcome flow that sends an email, waits, checks whether the person opened it, and then sends an SMS only to non-openers — inside one flow, no external sync required.
• Native Shopify data. Real-time sync of orders, products, checkouts, and catalog for dynamic content.
• Unified attribution. Klaviyo attributes email and SMS revenue in the same reporting model, so you're not stitching two dashboards together.

Klaviyo SMS is genuinely good. For most brands under a few hundred thousand subscribers, it's more than enough, and keeping SMS in the same platform as email removes an entire category of operational headaches.

Postscript

Postscript is a Shopify-native SMS platform. It doesn't do email. It doesn't run outside Shopify. What it does do, it does with real depth:

• US SMS/MMS deliverability focus — dedicated toll-free numbers, carrier compliance tooling, and short-link subdomains.
• Conversational commerce — two-way texting, reply management, and human/AI-assisted sales conversations over SMS.
• A visual flow builder with SMS-specific automation templates (cart abandonment, browse abandonment, welcome, upsell, shipping).
• Deep Shopify segmentation plus third-party integrations, including Klaviyo, so its flows can react to events happening elsewhere in your stack.

Postscript's whole pitch is "make SMS your #1 revenue channel." That's a real strategy for some brands — and overkill for others.

How the integration works

Here's the important mental model: the Klaviyo–Postscript integration is a bridge, not a merge.

When you connect Klaviyo to Postscript, Postscript can consume Klaviyo (and Shopify) events and use them to build segments and trigger SMS flows. Practically, this means:

• Event sharing. Behavioral signals — like a Klaviyo-tracked event or list membership — can inform who gets which Postscript text and when.
• Segment coordination. You can align audiences so the same customer isn't hammered by an email and a text for the same promo within minutes of each other.
• Suppression logic. You can use the connection to avoid double-messaging engaged subscribers across both platforms.

What it is not:

• It is not a single unified profile. The customer exists as a record in both systems.
• It is not shared reporting. Klaviyo reports Klaviyo revenue; Postscript reports Postscript revenue. You reconcile them yourself.
• It is not bidirectional flow orchestration. You can't build one flow that hops between the two platforms mid-sequence. Each platform runs its own flows.

If you understand that boundary going in, you'll avoid 90% of the pain brands report with this setup.

Step-by-step setup

Every brand's stack is slightly different, but the core sequence is consistent:

1. Confirm the prerequisites

• Active Shopify store (Postscript is Shopify-only).
• Active Klaviyo account with Shopify already connected.
• Admin access to both platforms.

2. Install and connect Postscript to Shopify

Install Postscript from the Shopify App Store first. Let it complete its initial Shopify sync (orders, customers, catalog) before touching Klaviyo. This gives Postscript its baseline data.

3. Connect Klaviyo inside Postscript

In Postscript, go to the integrations/apps area and add the Klaviyo integration. You'll authorize it with a Klaviyo API key. Use a private API key scoped to only what Postscript needs — don't paste a full-access key you can't rotate later.

4. Decide your channel-of-record for each flow

This is the step brands skip, and it's the most important one. For every core automation, pick one platform as the owner:

• Welcome / opt-in: usually split — email welcome in Klaviyo, SMS welcome in Postscript, coordinated so they don't fire simultaneously.
• Abandoned cart: decide whether email leads and SMS backs it up, or vice versa. Don't let both platforms independently text and email the same abandonment.
• Post-purchase / shipping: typically Klaviyo for transactional-style email, Postscript for SMS shipping updates if you use them.

Write this down. A one-page "who owns what" doc prevents the double-messaging that kills SMS opt-out rates.

5. Build suppression rules

Configure your segments so an engaged email subscriber isn't also blasted with the same-content SMS. Use the shared event data to suppress overlap. Over-messaging is the fastest way to spike unsubscribes and burn deliverability on both channels.

6. Test with a seed list

Before going live, run a small internal test list through both platforms for a real promo. Confirm timing, suppression, and that links and attribution are firing correctly.

Attribution: the part everyone gets wrong

When you run SMS on Postscript and email on Klaviyo, you now have two attribution models that don't talk to each other. Both will happily claim credit for the same order.

A customer might:

1. Get a Klaviyo email.
2. Get a Postscript text an hour later.
3. Buy.

Depending on each platform's attribution window and last-touch logic, both may report that revenue. If you naively add the two dashboards together, you'll overstate total performance — sometimes badly.

How to handle it:

• Set consistent attribution windows across both tools so you're at least comparing like with like.
• Pick a "primary" attribution source for board-level reporting, and treat the other as directional.
• Use UTM parameters and discount codes unique to each channel where you need clean, order-level truth.
• Sanity-check against Shopify. Shopify's own order data is the ground truth for actual revenue. If Klaviyo + Postscript claimed revenue exceeds a sane share of total Shopify revenue, your windows are double-counting.

If unified, clean attribution matters more to you than SMS depth, that alone is a strong argument for keeping SMS inside Klaviyo.

What it costs in 2026

You're paying for two platforms plus per-message SMS costs. Here's the real breakdown.

Postscript pricing (2026)

Postscript charges a monthly platform fee plus per-message rates on top of US carrier fees:

| Plan | Monthly fee | Per-SMS (US) | Notable | | --- | --- | --- | --- | | Starter | $0/mo ($49 minimum spend) | ~$0.009/SMS, $0.045/MMS | Dedicated toll-free number, 2 keywords | | Growth | $100/mo | ~$0.008/SMS, $0.03/MMS | Unlimited keywords, live chat support | | Professional | $500/mo | ~$0.007/SMS, $0.024/MMS | API access, enhanced analytics, branding removed | | Enterprise | Custom | Custom | Launch specialist, data warehouse push |

Carrier fees (roughly $0.0042/SMS and $0.0084/MMS in the US) are added on top of the per-message rate. Rates shown are for US 50-state/Canada sending.

Klaviyo cost

Klaviyo bills on your active profile count for its base plan (email), and SMS is billed as usage on top — you buy SMS/MMS sending credits, with US SMS commonly landing around a cent per message depending on volume and message length. The key point: with Klaviyo, SMS is an add-on to a platform you're already paying for, not a second full platform fee.

The honest math

Running both means you're paying:

• Your existing Klaviyo bill (email + any Klaviyo SMS you keep), plus
• A Postscript platform fee ($100–$500+/mo for most serious senders), plus
• Postscript per-message + carrier fees.

For a brand doing serious SMS volume where Postscript's tooling drives materially better performance, that stacks up fine. For a brand sending a few campaigns a month, you're paying a second platform fee for capability you won't use. Do the math on incremental SMS revenue Postscript actually unlocks versus just turning on Klaviyo SMS.

When to keep both vs. consolidate

Keep both if…

• SMS is (or is becoming) a top-3 revenue channel and you're sending high volume.
• You want Postscript's conversational commerce and reply-management depth.
• You have someone who owns SMS strategy specifically and can manage two platforms.
• Postscript's deliverability tooling measurably outperforms your Klaviyo SMS results in a real head-to-head test.

Consolidate on Klaviyo if…

• You want one customer profile and one attribution model.
• Your SMS program is early-stage or moderate volume.
• You value cross-channel flows (email + SMS in one automation) over SMS-specific depth.
• Ops simplicity and a lower total bill matter more than squeezing the last few points out of SMS.

For the majority of brands under significant scale, consolidating on Klaviyo is the right call — one platform, cleaner data, lower total cost, and SMS that's genuinely good enough. Reserve the two-platform setup for brands where SMS is a strategic pillar, not a nice-to-have.

Common mistakes

1. No channel-of-record plan. Both platforms independently message the same abandonment → customers get spammed → opt-outs spike.
2. Adding both dashboards together. Double-counted revenue makes your SMS program look better than it is and leads to bad budget decisions.
3. Skipping suppression rules. Engaged subscribers get hit twice with the same promo.
4. Over-scoped API key. Using a full-access Klaviyo key you can't easily rotate is an avoidable security risk.
5. Buying Postscript before testing Klaviyo SMS. Plenty of brands pay for a second platform to solve a problem native Klaviyo SMS would have handled.

FAQ

Does Postscript replace Klaviyo? No. Postscript is SMS-only and Shopify-only. It doesn't do email. If anything, Klaviyo can replace Postscript (with Klaviyo SMS), not the other way around.

Can I run email in Klaviyo and SMS in Postscript? Yes — that's the most common reason brands use the integration. Just plan channel ownership and suppression carefully.

Will the integration merge my customer profiles? No. Each customer exists as a separate record in each platform. It's a data bridge, not a unified profile.

Is Postscript worth it over Klaviyo SMS? Only if SMS is a serious, high-volume channel where Postscript's deeper tooling drives incremental revenue that exceeds the extra platform cost. For most brands, Klaviyo SMS is enough.

Does Postscript work outside Shopify? No. It's Shopify-only. If you're on another platform, this decision is moot — use Klaviyo SMS.

Getting help

Wiring up two platforms cleanly — channel ownership, suppression, attribution windows — is exactly the kind of thing where an experienced Klaviyo agency pays for itself, because the mistakes above quietly cost you revenue and subscribers.

If you want a vetted specialist rather than a guess, browse our directory of Klaviyo agencies. Every listing is a real, verified email-marketing and retention agency, and many handle SMS strategy and multi-platform setups like this one. Filter, shortlist, and reach out directly — no lead-selling middleman.

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Pricing and plan details reflect publicly listed 2026 figures and can change. Always confirm current rates directly with each vendor before making a decision.