SMS has quietly become one of the highest-ROI channels a DTC brand can run. The platform you pick shapes your list growth, your compliance risk, and how much of that revenue you actually keep.
Two names dominate the Shopify conversation: Postscript and Klaviyo. Postscript built its entire product around SMS and nothing else. Klaviyo folds SMS into the same CRM that already runs your email.
The stakes go beyond spend. SMS carries real compliance risk — a missing opt-in record or a carrier filtering flag can stall a whole program overnight. The platform's consent tooling and support quality matter as much as its creative features do.
This guide breaks both down across pricing, AI features, list growth, and real customer results. Find out which one fits where your SMS program stands right now.
Postscript vs Klaviyo: The Short Version
Postscript is the SMS specialist — an all-in bet on one channel, backed by AI tools purpose-built for texting. Klaviyo is the CRM brands already run for email, with SMS folded into the same customer profile.
The trade-off is depth versus consolidation. Pick Postscript for a dedicated SMS toolkit built around one channel. Pick Klaviyo to keep every channel under one login and one customer record.
- Postscript
- Starting price: $0/mo ($49/mo minimum spend)
- Model: SMS-only specialist
- Best for: Brands making SMS their top revenue channel
- AI features: Infinity Testing, Shopper, Brand Center
- List growth tools: Onsite Opt-in, CashBack, custom contact card
- SMS reach: Primarily US and Canada, Shopify-native
- G2 rating: 4.8/5 (161 reviews)
- Free trial: 30 days
- Klaviyo
- Starting price: Free plan; Email + SMS from $35/mo
- Model: Unified email + SMS CRM
- Best for: Brands scaling SMS on top of an existing Klaviyo email program
- AI features: K:AI Customer Agent, channel affinity, predictive CLV
- List growth tools: Signup forms tied to unified customer profiles
- SMS reach: 20+ countries
- G2 rating: 4.6/5 (1,361 reviews)
- Free trial: Free plan (150 SMS credits/mo)
1. Postscript: Built to Make SMS Your Top Channel
Postscript treats SMS as a business, not a feature bolted onto an email tool. The Scottsdale, Arizona-based company has grown to 251–500 employees, funded through a Series C led by 01 Advisors.
Its pitch to Shopify brands is blunt: "Not all-in-one, just all in." Every feature — flows, AI, list growth, compliance — exists to push a single channel further.
That focus shows in the client roster. True Classic, Thrive Causemetics, Dr. Squatch, Ruggable, and Death Wish Coffee all run SMS through Postscript.
What it's built for
Postscript's core stack starts with a visual flow builder and prebuilt automation templates. Every subscriber gets a dedicated toll-free number and a custom contact card. Replies then feel like texting a real business, not a shortcode.
Postscript AI bundles three tools: Brand Center, Infinity Testing, and Shopper. Infinity Testing replaces manual A/B tests with AI-generated message variants that keep improving. Shopper is a 1:1 AI shopping assistant that answers customer questions inside the same text thread.
The platform also ships RCS for richer, branded messaging, plus CashBack, a coupon alternative built for list growth. Onsite Opt-in pop-ups are pitched as converting 50% better than standard signup forms.
Plans and pricing
- Starter — $0/mo ($49/mo minimum spend)
- Per-message rate: $0.015 / $0.009 SMS, $0.045 MMS
- Built for: Brands just getting started with SMS
- Growth — $100/mo
- Per-message rate: $0.01 / $0.008 SMS, $0.03 MMS
- Built for: Brands building their SMS program
- Professional — $500/mo
- Per-message rate: $0.007 SMS, $0.024 MMS
- Built for: Brands scaling SMS as a top revenue channel
- Enterprise — Custom
- Per-message rate: Negotiated
- Built for: Brands making SMS their #1 channel
Every tier includes a 30-day free trial, and Postscript's own marketing cites a 4x ROI guarantee. Rates drop as you move up-tier, which rewards brands that commit rather than test lightly.
G2 reviewers flag the jump to Professional as steep. One reviewer called the $500 monthly platform fee hard to justify for a smaller list.
Pros and cons
Pros:
- 34x average ROI on SMS spend and a 4x ROI guarantee, per Postscript's own published figures
- Rated 4.8/5 on G2 across 161 reviews — among the highest-rated SMS platforms in the category
- Deep native Shopify data for segmentation, since Shopify is the primary integration target
- Postscript Plus adds a dedicated strategist, functioning like an in-house SMS hire
Cons:
- Per-message costs stack on top of the monthly fee, so pricing is harder to predict at volume
- Analytics stay basic; reviewers want deeper date-range and reporting tools
- Segmentation and list-exclusion options are more limited than a full CRM offers
- SMS-only for now — an email product is reportedly launching later this year, but it isn't live yet
Who's using it
Ruggable's retention team calls Postscript "a true extension of our team." Director Danae Young-Lagoeiro said they trust the account like an in-house hire, not a vendor.
Other reviewers report even sharper results. One G2 reviewer cited 60x ROI, and another reported six figures in sales within their first year on the platform.
2. Klaviyo: SMS Bundled Into a Public, $1.2B CRM
Klaviyo isn't an SMS specialist. It's a public company (NYSE: KVYO) that treats SMS as one channel inside a much bigger customer data platform. Klaviyo generated $1.234 billion in revenue in 2025, up 31.6% year over year, serving 193,000+ brands in 100+ countries.
For a brand already on Klaviyo for email, SMS is a checkbox away. Same customer profile, same segments, same flow canvas — no second tool to manage.
What it's built for
SMS runs on the same Klaviyo Data Platform as email. Every text pulls from shared purchase history, browse behavior, and predicted lifetime value. K:AI's Customer Agent can field pre- and post-purchase questions over SMS, escalating to a human when needed.
Channel affinity predicts which channel — SMS, email, or push — each customer actually prefers, so messages route accordingly. Send-time optimization for SMS is listed as "coming soon" as of this writing.
SMS is available in 20+ countries, including the US, UK, Australia, France, and Germany. That's well beyond Postscript's largely US and Canada footprint.
Beyond the SMS-specific tools, Klaviyo's Marketing Agent drafts full campaigns from a website URL and past performance. It's free on every plan. It's built mainly for email today, but sits inside the same platform SMS runs on.
Plans and pricing
- Free — $0/mo
- Included: 250 profiles, 500 emails/mo, 150 SMS credits
- Email — From $20/mo
- Included: 500 contacts, 5,000 emails/mo
- Email + SMS — From $35/mo
- Included: 251–500 contacts, 1,250 SMS/MMS credits
SMS and MMS credits bill by recipient country, bundled into the same plan price as email. There's no separate SMS invoice, unlike Postscript's per-message add-on. Pricing still climbs with list size, the same way it does on email-only plans.
Pros and cons
Pros:
- Backed by years of email and SMS performance data across 193,000+ brands
- One customer profile powers both channels — no duplicate segmentation work
- SMS bundled into the same invoice as email, with no separate platform fee
- Case studies show real SMS-specific lift, including Rebecca Minkoff's 23% year-over-year SMS revenue jump
Cons:
- SMS credits still cost extra as list size grows, even with unified billing
- Reviewers cite a steep learning curve for advanced flows and segments
- Some SMS-specific AI, like send-time optimization, still trails features already live at Postscript
- Brands with no existing email footprint gain less from the "one platform" pitch
Who's using it
Rebecca Minkoff saw a 23% year-over-year boost in SMS revenue within its first 70 days on the channel. Dagne Dover reported 12,000% ROI in year one, and Leonisa hit 45.6x ROI after switching to Klaviyo.
Culture Kings drove a 388% year-over-year jump in global SMS click rate. Across the platform, brands running email and SMS together see a 19% higher GMV growth rate than email alone.
Postscript vs Klaviyo: Head-to-Head
Pricing
Postscript's $0 Starter tier still carries a $49/month minimum spend. Klaviyo's Free plan has no such floor, and comes with 150 SMS credits built in.
At scale, the comparison flips. Postscript's per-message rate drops as low as $0.007 per SMS on its Professional plan. That reward structure favors brands sending high volume every month.
Klaviyo's SMS credits price by recipient country. They stack on top of contact-based tiers that already climb with list size — the same tiers used for email.
As a rough example: sending 20,000 texts a month costs Postscript's $500 fee plus about $140 in message charges. Call it $640 total.
A comparable Klaviyo Email + SMS plan at that contact size lands in a similar range. Credits price per recipient country rather than per message, though. That makes the two hard to compare directly.
AI and automation
Postscript's Infinity Testing replaces manual A/B tests with continuously improving AI variants. It's built specifically for SMS copy, not a whole marketing stack.
Klaviyo's K:AI spans more ground. Predictive CLV, churn scoring, and a Customer Agent already work across SMS, email, and WhatsApp.
List growth
Postscript's Onsite Opt-in claims a 50% higher conversion rate than standard popups. CashBack adds a coupon-based alternative built purely for SMS list growth.
Klaviyo folds signup forms into the same customer-profile system used everywhere else on the platform. A new SMS subscriber becomes instantly visible to email and paid-channel segmentation too.
Deliverability and reach
Postscript runs SMS through a dedicated toll-free number tied to Shopify. It's built primarily for the US and Canada, where most of its client base sells.
Klaviyo's SMS product covers 20+ countries, including the UK, Australia, France, and Germany. That reach matters for any brand selling beyond North America.
Both platforms also require standard carrier registration for US sending numbers. That step adds a few days to onboarding regardless of which platform you choose, so plan your launch date accordingly.
Ease of use and support
G2 reviewers rate Postscript's support as a standout. Several describe the team as a true extension of their own, not an outside vendor.
Klaviyo earns praise for its interface, but reviewers note response times can be inconsistent at scale. Both platforms draw complaints about the learning curve once you move past templates into custom flows.
Compliance and consent
Every SMS platform operating in the US has to manage TCPA consent. That means written opt-in before a marketing text goes out, plus an easy opt-out on every send. Both platforms build this into onboarding rather than leaving it entirely to the brand.
Klaviyo ships compliance guides, plus features like age-gating for regulated categories and transactional-consent management. Both tie back to the same customer profile. Postscript's compliance tooling centers on its dedicated toll-free number and opt-in flows built around Shopify checkout.
Neither platform removes the brand's legal responsibility for its own consent records. Whichever you choose, keep an independent audit trail of opt-ins separate from the platform itself.
Real results, side by side
- Postscript
- Ruggable — calls the account "a true extension" of its own retention team
- Platform-wide — 34x average ROI on SMS spend; 3x faster list growth than competitors
- Klaviyo
- Rebecca Minkoff — 23% YoY SMS revenue growth in its first 70 days
- Dagne Dover — 12,000% ROI in year one
- Leonisa — 45.6x ROI after switching platforms
- Culture Kings — 388% YoY increase in global SMS click rate
Individual results vary by list size, vertical, and how aggressively a brand sends. Treat platform-wide averages as a ceiling to aim for, not a guarantee on day one.
Common Questions About Postscript and Klaviyo
Is Postscript or Klaviyo better for SMS?
Postscript is the sharper pick if SMS is — or will become — your top revenue channel. It's a toolkit built only for texting.
Klaviyo is the better fit if you already run email through it. SMS then joins that same customer profile, without a second login.
Is Postscript cheaper than Klaviyo?
It depends on volume. Postscript's Starter plan requires a $49/month minimum spend before Klaviyo's comparable Free plan costs anything. But Postscript's per-message rate drops sharply at higher tiers, so heavy SMS senders may come out ahead over time.
Can I use Klaviyo for SMS without also using it for email?
Yes, but it's not where Klaviyo's pitch is strongest. The platform's real advantage is a unified customer profile feeding both channels. That only pays off once email and SMS run together.
Does Postscript offer RCS messaging?
Yes. Postscript added RCS for richer, branded messages sent from a verified business profile. RCS allows bigger images and buttons than standard SMS, though support still depends on the recipient's carrier and device.
What's the catch with Postscript's per-message pricing?
Every plan layers a per-SMS and per-MMS rate on top of the monthly fee. Brands with a large, active list can see costs climb quickly, even on lower tiers. Model your expected send volume before committing to a plan.
How long does it take to see ROI from SMS?
For Klaviyo specifically, G2's reviewer data puts average implementation at about a month. The average ROI timeline runs seven months.
Postscript doesn't publish an equivalent figure. Its 4x ROI guarantee implies a similar runway, since flow-tuning takes time to compound.
Can Needle work with Postscript or Klaviyo?
Needle already integrates directly with Klaviyo. It writes, designs, and launches email campaigns inside a brand's existing Klaviyo account, with no manual setup required.
Needle doesn't run SMS through Postscript directly. It handles the email and Meta ad creative that fills the gaps around whichever SMS platform a brand runs.
Conclusion: Postscript or Klaviyo?
If SMS is about to become your top channel, and Klaviyo doesn't run your email, Postscript's toolkit fits that bet. Infinity Testing, Shopper, and RCS all exist for one channel alone.
If you're already running email through Klaviyo, adding SMS keeps everything inside one customer profile and one invoice. That consolidation saves real operational overhead as your stack grows.
If you sell outside the US and Canada, Klaviyo's 20+ country SMS coverage is the more practical choice today. Postscript's toolkit is deep, but its reach is narrower.
If you're chasing the fastest AI-driven message testing, Postscript's Infinity Testing is the more mature, SMS-specific tool today. If your team already leans on Klaviyo's AI stack for email, extending it to SMS is the lower-friction path.
Either way, the platform is only half the job. Someone still has to write the campaigns, brief the creative, and keep the calendar moving every week — SMS included. Needle handles that layer: email through Klaviyo, plus the ad creative that drives traffic to your SMS list. See how Needle works and get your first campaign started.