14 Shopify SMS marketing apps: pricing, trade-offs, and a safe pilot

Consent, quiet hours, and purchaser suppression

Every SMS decision on this page sits on three operating controls. First, consent: TCPA plus state-level rules (California, Florida, Washington and others add their own wrinkles) require a documented opt-in source, timestamp, and disclosure text for every number — keyword, checkout checkbox, popup, and QR captures each create different expectations. Second, quiet hours: no promotional texts before 8am or after 9pm in the recipient's timezone, enforced by timezone-aware sending rather than a single store clock. Third, purchaser suppression: recent buyers exit promotional flows same-day across email and SMS, so nobody gets a cart nudge for the order they placed an hour ago.

Suppression also covers opt-outs (immediate, all channels), complaint-prone segments, holdout groups, and subscribers whose capture promise does not match the message you are about to send. Losing suppression history during a platform switch is the costliest migration failure — it manufactures complaints from previously happy subscribers. Review SMS consent basics and the TCPA and state-law guide before your next capture change.

• Log opt-in source, timestamp, and exact disclosure text at capture — never reconstruct retroactively
• Honor purchase exits same-day on shared profiles across email and SMS
• Enforce quiet hours per recipient timezone, including daylight-saving edge cases
• Keep STOP/HELP replies working on every sender ID; test them monthly

Margin math and app costs

SMS looks cheap per message until you subtract everything attached to it. A useful worksheet: incremental revenue per send, minus platform subscription, minus per-message carrier and surcharge fees, minus discount cost on redeemed codes, minus refunds and support replies. What survives is the number that matters — contribution margin per send. Stores that skip this math routinely pay more in app fees and discounts than the channel returns.

App costs also compound quietly: contact-tier growth, SMS credit packs, carrier pass-throughs on toll-free or short-code traffic, and add-on fees for premium features. Model the peak month (Black Friday, a product drop), not the average month, and compare that peak across stacks — see SMS pricing economics for the full worksheet.

Pricing deep-dive: what to verify before you commit

Pricing on this page is directional, not quotable — plans change often and carriers adjust surcharges several times a year. Before committing, check the official pricing pages for each app on your shortlist and confirm four things in writing: what the base tier includes, how overages are billed, which carrier fees are pass-through, and what happens to billing when your list grows 2x or 10x.

Then run a 30-day pilot at real volume with a holdout group. Attribute revenue conservatively (platform-reported attribution overstates lift), and report margin after all the cost lines above. A platform that wins at your current list size can lose at twice the size — re-run the model quarterly, and revisit the full app rankings when your send mix changes materially.

• Confirm base-tier inclusions, overage rates, and carrier pass-through fees in writing
• Model peak-month (not average-month) cost at 2x list size
• Pilot 30 days with a holdout; report margin after discounts, refunds, and support
• Re-check official pricing pages each quarter — numbers on review sites age fast

Decision table: which layer owns the job

Use this table to assign each message job to a channel and tool before shopping for software. Most Shopify stores fail by buying one platform to do everything, then letting frequency and consent discipline slip across all of them at once.

Frequency governance and holdout discipline

Frequency caps belong to the operator, not to whichever platform was bought last. Set a written cap per channel (most DTC brands hold promotional SMS to 2–4 sends per month), make purchase and support events exit every active queue immediately, and review opt-out rate per campaign type weekly — rising opt-outs on a stable list almost always means frequency, not creative, is the problem. Timezone-aware quiet hours (8am–9pm recipient-time) are part of the same contract; see the quiet hours guide for the edge cases.

Holdout discipline closes the loop. Reserve a small percentage of each segment from every major send, and judge programs on incremental margin against the holdout — not on platform-attributed revenue, which cannot distinguish a message that changed behavior from one that reached someone already on the way to checkout. The campaign restraint and offer discipline guides cover the full ritual.

1. Write the cap: promotional SMS slots, email sends, and combined touches per contact per week
2. Wire same-day purchase exits across both channels on shared profiles
3. Reserve a holdout slice from every broadcast above a set revenue threshold
4. Report opt-out rate and complaint keywords weekly by campaign type
5. Re-run the cost-and-margin worksheet quarterly at projected list size

Stack recipes by store stage

There is no single best stack — there are stage-appropriate ones. These are the defaults this site recommends, always subject to your own volume, consent operations, and a current read of each vendor's official pricing page.

Operator checklist before the next send

• Every recipient has a documented SMS opt-in source matching this message category
• Recent purchasers, open support tickets, and holdouts are suppressed
• Quiet hours pass for every destination timezone in the audience
• STOP and HELP replies verified on the current sender ID this month
• Margin worksheet updated: platform, carrier, discount, refund, support lines
• Channel calendar checked — no email offer colliding with this text within 12 hours
• Opt-out and complaint thresholds defined in advance with a stop rule

For matchup-level decisions, the head-to-head pages (start with Postscript vs Attentive and Klaviyo vs Omnisend) carry the same consent, suppression, and margin worksheets applied pairwise. If you are replacing a platform entirely, read the migration notes in the alternatives directory first — consent evidence migrates before anything else.