How to send back-in-stock alerts for ecommerce products by email and SMS

• Back-in-stock alerts work best when they track the exact product or variant, not just a product title or collection.
• Email suits richer restock messages with product images, names, prices and direct CTAs; SMS suits urgent alerts, but needs separate SMS consent.
• Omnisend, Klaviyo and Mailchimp document email and SMS back-in-stock options, but Mailchimp requires Shopify and Omnisend cannot insert dynamic product names into SMS.
• Brevo supports back-in-stock email alerts for Shopify, WooCommerce, Shopware 6, PrestaShop and API setups, but its official back-in-stock guide is email-focused.
• The real cost includes the plan, SMS credits, add-ons and expiry rules: Klaviyo and Mailchimp credits do not roll over, Omnisend credits expire after 60 days, and Brevo prepaid SMS credits never expire.

Back-in-stock alerts for ecommerce by email and SMS solve a simple problem: shoppers want something you cannot sell today. Instead of losing that demand, the store captures the product request and sends a notification when inventory returns.

The useful version is more precise than a generic restock newsletter. It knows which SKU, size, colour or bundle the shopper asked for, then sends them back to the right product page when the item is available.

This guide covers the setup, the consent work, the cost traps and the tool choice. It focuses on restock alerts only, not welcome flows, abandoned carts or broader email strategy.

What are back-in-stock alerts in ecommerce?

Back-in-stock alerts are product- or variant-specific notifications sent after an unavailable item becomes available again. They usually start with a “Notify me” button, form or widget on an out-of-stock product page.

The key detail is the product-contact association. The platform must store that a specific shopper asked about a specific variant, such as a medium black hoodie, not just hoodies in general.

Email gives you space for product images, price, copy and alternatives. SMS is faster and harder to miss, but it is shorter, more regulated and usually priced through credits or message segments.

How does the back-in-stock workflow actually work?

The workflow starts with inventory status. Your ecommerce platform, catalogue feed, plugin or API tells the marketing platform whether a product or variant is unavailable.

The “Notify me” form should only appear when the item cannot be bought. If it appears while checkout is still available, you may collect false demand and trigger alerts that make little sense.

The form collects email, phone number or both. Treat email and SMS consent separately, because a shopper who wants one restock email has not automatically agreed to receive SMS marketing.

Once the shopper submits the form, the system stores the product and contact together. That record is what lets the automation send the right product image, name, URL and variant details later.

The automation triggers when stock returns. A good setup then sends email, SMS or both, depending on consent, platform support and your message budget.

After the alert is sent, suppress or remove the completed association where the platform allows it. Brevo, for example, includes a step to remove the product-contact association after the back-in-stock email, which helps prevent duplicate alerts unless the contact subscribes again.

What should you prepare before you turn alerts on?

Start with platform support. Shopify, WooCommerce, BigCommerce, Magento, PrestaShop, Shopware, SFCC and custom catalogue setups are not covered equally by every tool.

Klaviyo has the broadest documented support among the tools covered here: Shopify, BigCommerce, Magento 2, PrestaShop, Shopware, SFCC, plus inventory-aware custom catalogue feed or API accounts. The trade-off is that Klaviyo can take more setup work than simpler Shopify-first options.

Mailchimp is narrower for this job. Its back-in-stock alerts require a connected Shopify store, so it is not the right choice if this feature must work across WooCommerce or a custom catalogue.

Check your inventory behaviour before testing. Omnisend warns that Shopify’s “Continue selling when out of stock” setting can make a product appear available and may trigger back-in-stock notifications.

Map product and variant IDs properly. A restock alert for the wrong size creates support tickets, refund requests and wasted SMS spend.

Plan the destination URL too. The alert should land the shopper on the exact restocked product or variant, not a collection page that forces them to hunt for it.

Should you send email, SMS or both?

Use email when the message needs product detail. A strong back-in-stock email can include the product image, name, price, variant, delivery note and a clear button back to the product page.

The downside is speed. Email can sit unread while a limited restock sells through, especially for popular SKUs or small replenishment batches.

Use SMS when speed matters and the customer has explicitly opted in. It suits limited drops, high-demand products and replenishments where the first few hours matter.

The catch is cost and length. Klaviyo says SMS messages are up to 160 characters, or 70 characters with emoji or special characters, and longer messages are split into multiple segments.

If you use both, keep them in one flow where the platform supports it. Klaviyo recommends using email and SMS together in one back-in-stock flow rather than maintaining a separate SMS-only flow.

Do not send both channels to everyone by default. Use consent and value as the filter, because a low-margin product can lose its profit if every request triggers several paid messages.

Which tools support back-in-stock alerts by email and SMS?

Among the marketing tools in our fixed ranking, the order is Omnisend, Klaviyo, Mailchimp, then Brevo. That order matters, but the right choice depends on your store platform and the exact SMS behaviour you need.

Omnisend supports a Back in Stock form and automation. The form appears on out-of-stock product pages, and the automation preset notifies customers when products are restocked.

Omnisend’s default back-in-stock email includes a dynamic Back in Stock item that displays product information. The limitation is SMS: Omnisend can include SMS in the automation, but dynamic event data such as specific product names cannot be used in SMS messages.

Omnisend is useful if you want a Shopify-focused restock setup with demand reporting. Its reports show products customers are waiting for, request counts, last request dates and contact details such as email, phone, country and request date.

Klaviyo is the strongest documented option here if you need multi-platform support or custom catalogue support. It has a Back in Stock Delay component that is unique to back-in-stock flows.

Klaviyo also supports SMS in back-in-stock flows, provided SMS is enabled and recipients are current SMS subscribers. For supported ecommerce integrations, SMS can use event variables and catalogue tags for details including title, image, URL, price and variant data.

Mailchimp can work if your store is on Shopify and you already use Mailchimp. Its setup requires both a back-in-stock form and a back-in-stock automation to be active.

Mailchimp templates cover email only, SMS only, and both email and SMS. The downside is that SMS requires SMS Marketing setup, a paid marketing plan, approval and purchased SMS credit blocks.

Brevo supports product alerts for Shopify, WooCommerce, Shopware 6, PrestaShop and API setups. It offers a pre-built Product is back in stock automation, with email personalisation through a data feed for product image, name and price.

Be precise with Brevo. It has prepaid SMS credits as a broader add-on, but its official back-in-stock guide documents automated email alerts rather than a built-in email-plus-SMS restock workflow.

How much do back-in-stock alerts cost?

The cost is not just the monthly subscription. Model the plan price, feature access, SMS add-ons, credit expiry, country mix, MMS usage and likely restock request volume.

Omnisend Standard starts at $16/month in our site data. Its Free plan has up to 500 emails/month to a maximum of 250 unique contacts, but new paid users who subscribed on or after May 4, 2026 need Pro to send SMS campaigns or automations.

Omnisend’s latest Pro SMS rates start at $0.007 per message, according to its May 2026 update. The catch is credit expiry: Omnisend says SMS credits expire after 60 days, with unused credits rolling over only to the next 30 days.

Klaviyo starts at $20/month in our site data. Its Free plan includes up to 250 profiles, 500 emails/month and 150 mobile message credits/month, but mobile credits do not roll over.

Klaviyo’s credit maths depends on message type and length. In the US, 1 SMS costs 1 credit and 1 MMS costs 3 credits, and longer or special-character messages can consume more segments.

Mailchimp Essentials starts at $13/month in our site data. Its Free plan allows up to 250 contacts and 500 sends/month, with a daily send limit of 250.

Mailchimp SMS Marketing is available in select markets with a paid marketing plan. Credits are bought in blocks, automatically repurchase monthly and expire each month without rollover, so unused credits are a real cost.

Brevo Starter starts at $9/month in our site data, and Standard starts at $18/month. Brevo’s pricing page lists back-in-stock alerts under Professional, which starts at $499/month, so do not assume the $9 tier covers this specific feature.

Brevo prepaid SMS credits are available as an add-on on all plans, start from 100 credits and never expire. That is useful for irregular restocks, but it does not change the email-focused nature of Brevo’s documented back-in-stock workflow.

How should you build the actual alert?

Start with one out-of-stock SKU and build the flow around it. A narrow test catches variant mapping, consent and trigger issues before they affect a high-demand product.

Enable the out-of-stock widget or form, then decide whether to collect email only, SMS only or both. If you collect both, write consent language that makes the SMS opt-in clear and separate.

Pass the product ID and variant ID into the automation. If those fields are missing, the platform may know who asked for an alert but not what they asked for.

Design the email around the requested product. Include the image, product name, price and a direct CTA to the exact product or variant page.

Keep the SMS short. A practical version says the item is back, names it where the platform supports that safely, and includes a direct link.

Add suppression logic after the alert. If the same contact should only receive one notification for that restock, remove or suppress the product-contact association after sending.

Then test the full loop. Submit the form as a shopper, restock the SKU, confirm the trigger fires, check the channel split and click through to the product page.

What are the mistakes that break restock alerts?

The most common mistake is sending a generic restock email. If the shopper cannot see the product they requested, the alert feels like a campaign, not a service.

The second mistake is triggering the wrong variant. This is common when products have sizes, colours, bundles or regional SKUs that share a parent product.

Consent is another weak spot. Email opt-in and SMS opt-in are different, and treating them as interchangeable can create compliance and trust problems.

SMS credit buying needs the same care as creative work. Klaviyo and Mailchimp credits do not roll over, Omnisend credits expire after 60 days, and Brevo prepaid SMS credits never expire.

Shopify inventory settings also deserve a test. If “Continue selling when out of stock” is enabled, the product may not behave like a normal unavailable SKU in every restock flow.

The final mistake is choosing a tool for the wrong platform. Mailchimp may be fine for Shopify restock alerts, but it is the wrong answer if you need documented WooCommerce support for this exact feature.

Which setup should you choose?

Choose Omnisend if you want a strong ecommerce marketing tool with a built-in Back in Stock form, automation and demand reporting. It is less suitable if your SMS copy must dynamically include the specific product name.

Choose Klaviyo if platform coverage and SMS personalisation matter more than simplicity. It is the best-documented option here for multi-platform and custom/API catalogue setups, but it may be more involved to configure.

Choose Mailchimp if you are on Shopify, already use Mailchimp and need a basic email/SMS restock path. Avoid it for this job if your store is on WooCommerce, BigCommerce or a custom catalogue.

Choose Brevo if you need back-in-stock email alerts across Shopify, WooCommerce, Shopware 6, PrestaShop or API setups, and SMS expiry rules are important elsewhere in your stack. Do not choose it expecting a documented built-in email-plus-SMS back-in-stock automation.

For most stores, the right first step is email-only on one high-demand SKU. Add SMS once the variant mapping, consent language and margin maths are proven.

Frequently asked questions

Can Shopify stores send back-in-stock alerts by email and SMS?

Yes, Shopify stores can use tools such as Omnisend, Klaviyo and Mailchimp for documented back-in-stock email and SMS workflows. Check Shopify inventory settings first, especially “Continue selling when out of stock”, because it can affect whether an item appears unavailable or restocked.

Can WooCommerce stores send back-in-stock alerts?

Yes, but tool choice matters. Brevo documents product alerts for WooCommerce, and Klaviyo supports back-in-stock flows for several platforms and inventory-aware custom setups. Mailchimp’s documented back-in-stock alerts require Shopify, so it is not the fit for WooCommerce restock alerts.

Which tool is best if SMS personalisation matters?

Klaviyo is the strongest documented option here if SMS personalisation matters, because it supports event variables and catalogue tags for product title, image, URL, price and variant data on supported integrations. Omnisend can include SMS, but its guide says dynamic event data such as product names cannot be used in SMS messages.

Can I send back-in-stock alerts on a free plan?

Sometimes, for testing or tiny volumes. Omnisend, Klaviyo, Mailchimp and Brevo all have free-plan limits, but feature access, contacts, sends and SMS credits can block real use. Brevo’s pricing page lists back-in-stock alerts under Professional, which starts at $499/month.

Do SMS credits expire?

It depends on the provider. Klaviyo and Mailchimp mobile or SMS credits do not roll over, Omnisend SMS credits expire after 60 days, and Brevo prepaid SMS credits never expire. That expiry rule can matter more than the headline plan price for irregular restocks.

Do I need separate SMS consent for back-in-stock alerts?

Yes. Treat SMS consent separately from email consent. A shopper entering an email address for a restock notice has not automatically opted in to SMS, and platforms that support SMS restock alerts still require recipients to be valid SMS subscribers.