Quick answer
No winner yet. Klaviyo and Postscript differ most in architecture and intended operating model. Use this researched comparison to decide which deserves a hands-on pilot—not as a substitute for one.
At a glance
| Decision factor | Klaviyo | Postscript |
|---|---|---|
| Billing model | Prepaid dollar plan, carrier fees included | Monthly fee + per message + carrier fees |
| 5,000 US SMS/month | $70 | $61.50 (Starter: 5,000 × ($0.009 + $0.0033)) |
| 20,000 US SMS/month | $240 | $246 (Starter) |
| 5,000 US MMS/month | $200 | $264.95 (Starter) |
| Included in the platform (billed by active profiles) | Waitlist only | |
| Free entry | $5 of mobile messages/month on the free plan | $100 trial credit for 30 days |
| Dedicated short code | Recommended above 95,000 recipients/month; price not published | $750/month |
Architecture and target user
Klaviyo
An email and SMS platform for ecommerce. Since July 13, 2026, SMS and MMS are bought as a prepaid monthly dollar plan with per-message rates that include carrier fees.
Worth investigating for brands that want email and SMS in one platform with shared profiles, segments and flows.
Postscript
SMS marketing built for Shopify brands, with plans that combine a monthly fee and per-message rates, plus carrier fees passed through at cost.
Worth investigating for Shopify brands that treat SMS as a primary channel and want SMS-specific tooling and plans.
Ease and implementation considerations
Klaviyo
Add a mobile-messaging plan to a Klaviyo account and set up a sending number. Klaviyo recommends a short code for sending to more than 95,000 people a month, at additional cost.
Postscript
Install on Shopify and choose a plan. A dedicated short code costs $750/month. Postscript's email product is waitlist-only, so email stays elsewhere.
These are research observations, not timing or usability test results. Implementation depends on catalog, data migration, design, channels, integrations, internal skills, and partner scope.
Ecosystem and integrations
Klaviyo
Email, SMS, MMS, WhatsApp and RCS from one profile, plus add-ons such as reviews and a helpdesk. The free plan includes $5 of mobile messages a month.
Postscript
SMS and MMS for Shopify; Postscript lists average US carrier fees on its pricing page and an AI plan at $699/month.
Pricing approach
Klaviyo: Prepaid monthly dollar plan; unused spend doesn't roll over. Klaviyo's calculator showed US toll-free SMS at $15 for 1,000 messages, $70 for 5,000, $125 for 10,000 and $240 for 20,000; MMS at $45 for 1,000, $200 for 5,000 and $385 for 10,000. Carrier fees included. Email is billed separately by active profiles. Checked Oct 7, 2026.
Current Klaviyo pricingPostscript: Starter $0/month with a $49 monthly minimum spend, $0.009 per SMS and $0.045 per MMS; Growth $100/month, $0.008 and $0.03; Professional $500/month, $0.007 and $0.024; Enterprise custom. Carrier fees are extra (Postscript lists averages of $0.0033 per SMS and $0.00799 per MMS). $100 trial credit for the first 30 days. Checked Oct 7, 2026.
Current Postscript pricingEditorial calculation from each vendor's pricing page, Oct 7, 2026. Klaviyo figures are its calculator's US toll-free examples; Postscript's carrier fees are its published US averages, so real totals vary. Sender type (toll-free, short code) affects deliverability and cost on both.
Build a scenario-based total-cost model. Include implementation, ongoing labor, extensions, communications or payments, support, and migration—not only the published base price.
Which businesses should investigate each
Investigate Klaviyo if…
- You already use Klaviyo for email and want SMS on the same profiles and flows.
- You send a lot of MMS, where Klaviyo's listed rates were lower in our example.
- You want carrier fees included in a single per-message price.
Investigate Postscript if…
- SMS is a primary channel and you want an SMS-specialist platform on Shopify.
- You send mostly SMS rather than MMS at small to mid volumes.
- You're comfortable keeping email in a separate tool.
What we still need to test
- Send the same campaign to matched audiences and reconcile each invoice against the published rates.
- Compare deliverability by sender type (toll-free vs short code).
- Compare flow setup and segment sharing with your email program.
BestStorefront will not name a winner before those scenarios are completed and documented.
Decision support
Frequently asked questions
Is Klaviyo SMS cheaper than Postscript?
It depends on the mix. In our example, 5,000 US SMS cost about $70 on Klaviyo and $61.50 on Postscript Starter; at 20,000 SMS they were within $6. For MMS, Klaviyo's listed price was lower ($200 vs about $265 for 5,000).
Does Klaviyo charge carrier fees for SMS?
Klaviyo says its per-message rates include carrier fees since its July 2026 switch to prepaid dollar plans. Postscript charges carrier fees on top, at cost.
Can Postscript send email?
Not yet for most brands: Postscript's pricing page lists email as waitlist-only.