Email gets opened by about 20 to 25% of the people who receive it. SMS gets opened by 90 to 98%, with 80% of messages read within five minutes of delivery (Sakari, 2025). That is not a marginal difference. It is a structural one. SMS reaches customers in a way that no other marketing channel matches, because a text message arrives in the same place as messages from their friends and family, and it demands attention in a way that an email sitting in a crowded inbox does not. For Shopify merchants, SMS is also one of the most underused channels in the stack. Most stores have email marketing running. Far fewer have SMS set up correctly, compliantly, and optimised for conversion. This article covers how to do all three: build a compliant SMS programme from the ground up, send at the right times, and turn the open rate advantage into actual revenue.

Why SMS Performs the Way It Does

Understanding why SMS converts at the rates it does is useful before building a strategy around it, because it clarifies which types of messages deserve the channel and which do not.

The performance advantage of SMS comes from three structural factors. First, SMS bypasses the inbox entirely. Email inboxes are filtered, sorted, and routinely ignored. A text message arrives as a notification that the recipient actively has to dismiss or engage with. The open rate reflects this: there is almost no passive ignoring of SMS the way there is with email.

Second, SMS is consumed immediately. The average email is opened hours after delivery. The average text message is read within 3 to 5 minutes (Sakari, 2025). For time-sensitive messages, flash sales, back-in-stock alerts, abandoned cart nudges, delivery updates, that speed is operationally significant. A customer who sees a back-in-stock alert for a product they wanted within minutes of it restocking is in a fundamentally different conversion context than one who sees the same alert six hours later.

Third, SMS has not yet been saturated the way email has. The average person receives dozens of marketing emails per day. Marketing texts from brands are still relatively infrequent, which means each message carries more relative weight and attention. Surveys from 2024 to 2025 show that companies using SMS marketing are nearly six times more likely to report digital marketing success than those that do not (Sakari, 2025).

ROI data supports the channel's commercial performance. Returns sit between $21 and $41 for every $1 spent on SMS marketing, with some seasonal campaigns during peak periods reporting up to $71 per dollar (Sakari, 2025). Email's widely cited ROI of $42:1 (Brenton Way, 2026) is the benchmark for comparison. SMS is at or above that level for well-optimised programmes.

The Compliance Foundation: What You Cannot Skip

SMS marketing operates in a heavily regulated environment in the US, and the consequences of getting it wrong are not abstract. In 2025 alone:

  • Clover Network settled a TCPA class action for $15 million for sending over 1 million unsolicited marketing texts

  • Cash App settled for $12.5 million for referral programme texts sent without clear consent

  • Zales Jewelers settled for $7.5 million for SMS marketing violations

  • DSW / Designer Brands settled for $4.42 million for continuing to send marketing texts after consumers opted out (Bloomreach, 2026)

The Telephone Consumer Protection Act (TCPA) carries statutory penalties of $500 to $1,500 per message sent without proper consent. Send an off-hours campaign to 1,000 subscribers without consent and you are looking at potential liability of $500,000 to $1.5 million from a single send. Class action lawsuits compound this, the cost per message applies per recipient, and TCPA class actions are among the most common consumer protection lawsuits in the US (TxtCart, 2026).

Compliance is not a legal department problem for large brands. It is a table stakes operational requirement for any Shopify merchant running SMS, at any volume.

What TCPA Requires

Prior express written consent before any promotional SMS. You must have documented, affirmative consent from each subscriber before sending any marketing text. Consent cannot be implied from a previous purchase. It cannot be buried in terms of service. It cannot be a pre-checked box. The consent mechanism must make clear what the customer is signing up for: marketing texts, the frequency, and the ability to opt out at any time (Voxie, 2025).

A compliant opt-in form includes language such as: "By providing your phone number and checking this box, you consent to receive marketing text messages from [Store Name] at the number provided. Message frequency varies. Message and data rates may apply. Reply STOP to opt out at any time." Every element of that language is a legal requirement, not a suggestion.

Transactional messages are different from promotional messages. Order confirmations, shipping notifications, and delivery updates are transactional. They can be sent 24 hours a day as long as they contain no promotional content. The moment a transactional message includes an offer, "Your order has shipped! Here's 10% off your next purchase", it becomes a promotional message and must comply with all promotional SMS rules including sending-hour restrictions (TCPA Compliance guide, Digital Applied, 2026).

Opt-out must be immediate and complete. When a customer replies STOP, that opt-out must be processed and all future promotional messages must cease. Since April 2025, the FCC requires businesses to accept opt-out requests through any reasonable method, not just the STOP keyword reply. This includes email, phone calls, website forms, and in-person requests. Opt-outs must be processed within 10 business days. Continuing to send messages after a STOP request is among the most commonly litigated TCPA violations (Bloomreach, 2026).

Quiet hours apply based on the recipient's time zone, not yours. TCPA prohibits promotional SMS before 8 AM or after 9 PM in the recipient's local time. If you send a campaign from California at 6 PM, it arrives in New York at 9 PM, exactly at the legal boundary. Best practice is to cut off campaigns at 8 PM recipient time to build in a buffer for time zone calculation errors. State law adds additional restrictions: Texas Senate Bill 140, effective September 2025, restricts unsolicited messages between 9 PM and 9 AM Monday through Saturday with tighter Sunday rules (TxtCart, 2026).

10DLC registration is mandatory in the US. 10-digit long code (10DLC) registration is the carrier-level compliance requirement for business SMS in the US. Unregistered SMS traffic is filtered and increasingly blocked by major carriers. Registration requires submitting your brand information and the campaign use case to The Campaign Registry. Every Shopify merchant sending SMS in the US must complete this registration before launching any campaigns. SMS platforms including Klaviyo, Attentive, and Postscript handle 10DLC registration as part of onboarding, but you need to complete the process before your first send.

GDPR applies to EU subscribers. If any of your subscribers are EU residents, GDPR adds a lawful basis requirement on top of TCPA-style opt-in rules. SMS marketing to EU subscribers almost universally requires explicit consent under GDPR, not a soft opt-in, not a pre-checked box, not consent bundled into terms of service. Each subscriber must have actively and specifically consented to receive marketing texts from your store. Withdrawal must be as easy as giving consent. A STOP reply must result in complete cessation of promotional messages from all channels that the subscriber opted out of (Digital Applied, 2026).

Building Your SMS Subscriber List on Shopify

A compliant subscriber list is built through opt-in mechanisms that are transparent, clearly disclosed, and attached to a genuine value exchange. Buying lists, importing contacts who have not explicitly opted into SMS, or adding SMS opt-in by default to checkout are all non-compliant approaches that create TCPA exposure.

The opt-in mechanisms that produce the highest-quality, highest-converting subscriber lists for Shopify merchants:

Checkout opt-in with explicit disclosure. Adding an unchecked SMS opt-in checkbox to Shopify's checkout, below the phone number field, with clear disclosure language is the highest-volume subscriber acquisition method for most stores. It captures subscribers at the moment of highest brand engagement and produces a list of customers who have already demonstrated purchase intent. The checkbox must be unchecked by default. The disclosure must be visible and specific. This is the method used by most major Shopify SMS platforms and is the starting point for most merchants.

Pop-up opt-in with a lead magnet. An exit-intent or time-delayed pop-up offering a discount (typically 10 to 15% off) in exchange for a phone number and SMS consent. This works well for first-time visitors who have not yet purchased. The conversion rate on SMS pop-ups varies significantly by offer and timing, but well-optimised pop-ups can build subscriber lists quickly from organic traffic. The pop-up must include full disclosure language and must not pre-check any consent boxes.

Keyword opt-in. Promoting an SMS keyword ("Text JOIN to 12345 for exclusive deals") on product packaging, email footers, social profiles, and in-store signage. The customer initiating the text to your number is itself an affirmative opt-in action, which simplifies the consent documentation. This method works well for brands with strong existing audiences across multiple channels.

Post-purchase opt-in in the thank you email. Including an SMS opt-in invitation in the order confirmation email, with a link to a dedicated SMS consent page. Customers who just completed a purchase are in a high-engagement state and more likely to opt in than cold traffic.

Timing: When to Send for Maximum Engagement

Timing is the most consistently underestimated variable in SMS performance. The difference between a message sent at the optimal time and the same message sent two hours earlier or later can be 20 to 30% in open and click rate, because SMS is consumed in real time and recipient context matters more than with email.

The highest-performing send windows for promotional SMS:

  • Tuesday through Thursday, 10 AM to 12 PM recipient local time. Mid-morning captures subscribers after their morning routine when they are actively on their phones but not yet in the distraction of the afternoon. Weekend send rates are lower for most categories because customers are in different contexts.

  • Thursday 6 PM to 8 PM for weekend sale announcements. The customer is planning their weekend when the message arrives, which makes purchase consideration timing-appropriate.

  • Sunday 6 PM to 8 PM for the start-of-week push. Many merchants report strong performance on Sunday evenings when customers are relaxing and more receptive to browsing.

The worst-performing send windows:

  • Before 9 AM any day, messages arriving before the customer's morning routine is established feel intrusive and generate higher opt-out rates

  • After 8 PM, approaching quiet hours and associated with evening wind-down contexts where purchase conversion is lower

  • Monday mornings, customers managing Monday obligations convert poorly from promotional SMS

Triggered messages perform differently from broadcast campaigns. Abandoned cart SMS, back-in-stock alerts, and post-purchase follow-ups are triggered by customer behaviour rather than a broadcast schedule. These messages should be sent within the optimal window closest to the triggering event, not at a fixed time. An abandoned cart SMS sent 30 minutes after abandonment, during business hours, consistently outperforms the same message sent the following morning regardless of timing.

Frequency discipline matters more than timing. Over-messaging is the primary driver of SMS opt-outs. Industry data shows that 2 to 4 promotional messages per month is the optimal range for most Shopify merchants. Above 6 messages per month, opt-out rates increase significantly and subscriber list quality degrades. Every SMS platform shows unsubscribe rate by campaign, if any campaign generates an opt-out rate above 3%, the message, timing, or frequency is wrong and needs adjustment before the next send.

The SMS Campaigns That Convert for Shopify Merchants

Not every marketing message deserves the SMS channel. SMS is the highest-attention channel you have access to, which means it should carry your highest-urgency, highest-relevance messages. Using it for generic promotional content wastes subscriber attention and erodes the channel's performance over time.

The specific SMS campaign types that consistently produce the highest conversion rates for Shopify merchants:

Abandoned cart recovery. Customers who added to cart and left without purchasing are the highest-intent segment available. An abandoned cart SMS sent 30 to 60 minutes after abandonment, concise and direct, with a link back to their cart, recovers a meaningful percentage of carts from subscribers who missed or ignored the email. The SMS recovery sequence typically runs after the email: email at 1 hour, SMS at 3 to 4 hours if no purchase has been made. The combined recovery rate for email plus SMS abandoned cart sequences exceeds either channel alone.

Flash sale announcements. Time-limited offers with a genuine deadline perform well through SMS because the immediacy of the channel matches the urgency of the message. A flash sale running for 24 hours, announced via SMS with the exact end time stated, converts better than the same announcement via email because the recipient acts in the moment of reading rather than planning to return later.

Back-in-stock alerts. For customers who have waitlisted a product or previously viewed a sold-out item, a back-in-stock SMS is the highest-converting triggered message available. The customer already expressed interest. The text arrives minutes after restocking. The conversion window is narrow, popular products sell out again quickly, which creates genuine urgency. Open rates and click rates on back-in-stock SMS consistently exceed all other campaign types.

VIP early access. Giving your SMS subscribers early access to new product launches or sale events, ahead of email subscribers and public announcements, rewards the opt-in and reinforces the value of subscribing. This creates a positive association with your SMS messages that reduces opt-out rates and increases anticipation of the next message.

Delivery updates. Order shipped, out for delivery, and delivery confirmed texts are transactional but perform a CRO function: they reduce the "where is my order" support tickets that consume merchant time and reduce customer anxiety between purchase and delivery. Many merchants find that proactive delivery updates measurably reduce inbound support volume on the days following large sends.

Choosing an SMS Platform for Shopify

The SMS platform you choose affects your deliverability, your compliance infrastructure, and your ability to integrate with Shopify's order and customer data. The platforms most widely used by Shopify merchants in 2026, and where each fits:

Klaviyo is the choice for merchants who want email and SMS in a single platform with shared subscriber data, segmentation, and automation. If you are already using Klaviyo for email, adding SMS does not require a separate platform, a separate subscriber import, or separate segmentation logic. Klaviyo's SMS is deeply integrated with Shopify's order and customer data, which enables behavioural triggers (abandoned cart, back-in-stock, post-purchase) to fire on the same conditions as email flows. The pricing model is per-message, which keeps costs aligned with actual usage rather than a fixed monthly fee.

Attentive is the dedicated SMS platform of choice for merchants who prioritise list growth and subscriber acquisition. Attentive's two-tap mobile opt-in technology, which makes subscribing from a mobile browser a single action requiring no form completion, generates significantly higher conversion rates on pop-up and inline opt-in placements than standard form-based approaches. Used by 33.4% of top Shopify stores (OptiMonk, 2026), Attentive is particularly strong for high-growth brands where subscriber acquisition speed is a priority.

Postscript is built specifically for Shopify and is the most natively integrated SMS platform in the ecosystem. Its subscriber segmentation uses Shopify customer data directly, purchase history, product categories, order value, location, without requiring manual data imports or third-party integrations. For merchants who want detailed SMS campaign analytics mapped against Shopify revenue attribution, Postscript provides the clearest picture of SMS-generated revenue per campaign.

TxtCart is the best fit for merchants focused primarily on conversational abandoned cart recovery. TxtCart's two-way SMS system allows customer-facing agents (human or AI) to have real SMS conversations with abandoners, answering product questions and overcoming objections in real time. For high-AOV categories where purchase hesitation is the primary abandonment driver, conversational recovery through TxtCart consistently outperforms one-way broadcast recovery messages.

Measuring SMS Performance: The Metrics That Matter

SMS performance measurement in 2026 goes beyond open rate. With deliverability increasingly becoming a compliance problem as well as a technical one, the metrics worth tracking:

Delivery rate. The percentage of messages sent that were successfully delivered to recipients. Anything below 95% signals list quality problems (inactive numbers, invalid numbers) or carrier filtering issues from 10DLC registration problems. A delivery rate below 90% requires immediate investigation.

Click-through rate. The percentage of delivered messages that resulted in a link click. Benchmark for promotional SMS: 18 to 35% (Sakari, 2025). Below 10% on a promotional campaign indicates the message, offer, or audience segment was poorly matched.

Conversion rate. The percentage of recipients who completed a purchase after clicking. This requires proper UTM tracking on all SMS links. Without attribution tracking, you are measuring clicks but not revenue.

Opt-out rate per campaign. The percentage of recipients who unsubscribed after each message. Above 3% on any campaign is a warning signal. Consistently above 2% across campaigns indicates over-messaging or poor offer relevance.

Revenue per subscriber per month. The total SMS-attributed revenue divided by the active subscriber count, measured monthly. This is the metric that captures the commercial value of the channel and should be tracked alongside the cost per message to calculate true SMS ROI.

For Shopify merchants running SMS for the first time, the 90-day benchmark targets to aim for: delivery rate above 96%, click-through rate above 15%, opt-out rate below 2%, and at least 2 promotional campaigns per month with a clear revenue attribution measurement for each.