How to Add Back-in-Stock Notifications on Shopify

A sold-out product page is not a dead end — it is an opportunity. Every visitor who lands on an out-of-stock product is a qualified buyer with purchase intent. Without back-in-stock notifications, you lose them. With them, you capture their email, build your list, and recover the sale when you restock.

Back-in-stock notification emails consistently outperform standard marketing emails. We see 10-15% conversion rates on these emails across the stores we manage — compared to 1-3% for typical promotional campaigns. The intent is already there; the notification simply completes the loop.

This guide covers three approaches to implementing back-in-stock notifications on Shopify: using Klaviyo (our recommended approach), using a dedicated app, and building a custom solution.

Why back-in-stock notifications matter

The commercial case for back-in-stock notifications is straightforward:

• Revenue recovery. Every sold-out product that has demand represents lost revenue. Notifications capture that demand and convert it when inventory returns.
• List building. Visitors who sign up for notifications are high-intent prospects. Even if they do not purchase immediately, they are now on your email list for future marketing.
• Demand intelligence. Notification signups tell you exactly which products have waiting demand. This data informs purchasing decisions and helps prevent future stockouts.
• Customer experience. A "Notify me" button is far better than a disabled "Add to cart" button. It gives customers a clear next step rather than a dead end.
• SEO preservation. Sold-out product pages still receive organic traffic. Back-in-stock notifications capture that traffic's value rather than letting it bounce.

For stores that regularly sell out of popular items — particularly fashion, beauty, and limited-edition brands — back-in-stock notifications can add 5-15% to monthly revenue.

Your three options

Approach	Best for	Cost	Complexity
Klaviyo integration	Stores already using Klaviyo	Included in Klaviyo plan	Low
Dedicated app	Stores not on Klaviyo	Free-£20/month	Low
Custom build	Stores needing full control	Development time	High

For most Shopify stores, Klaviyo is the best option because it integrates back-in-stock notifications into your broader email marketing strategy. The notification becomes part of the customer journey, not an isolated function.

Option 1: Set up with Klaviyo (recommended)

Klaviyo's back-in-stock feature is built into the platform. If you are already using Klaviyo for email marketing, enabling it takes about 30 minutes.

Step 1: Enable the back-in-stock feature

1. In Klaviyo, go to Flows
2. Click Create Flow
3. Search for "Back in Stock" in the flow library
4. Select the Back in Stock pre-built flow
5. Choose the Shopify integration as the catalogue source
6. Click Create Flow

Step 2: Add the signup form to your theme

Klaviyo provides a snippet of code to add to your product page template. This displays a "Notify me when available" button when a product or variant is out of stock.

1. In Klaviyo, go to Back in Stock > Settings
2. Copy the embed code snippet
3. In your Shopify theme editor, open the product template file (usually sections/main-product.liquid or similar)
4. Find the add-to-cart button section
5. Add the Klaviyo snippet, wrapped in a conditional that only shows it when the product is sold out:

{%- if product.available == false -%}
  <!-- Klaviyo Back in Stock button -->
  <div class="klaviyo-bis-trigger"
       data-item="{{ product.selected_or_first_available_variant.id }}">
  </div>
{%- endif -%}

{%- comment -%}
  For variant-level tracking, update the data-item
  attribute when the customer selects a different variant
{%- endcomment -%}

Step 3: Configure the flow

Customise the back-in-stock flow in Klaviyo:

• Trigger — set to fire when the product variant is back in stock
• Timing — send immediately when restocked (do not add delays)
• Email content — design a focused email with the product image, name, price, and a direct link to the product page
• Filters — exclude customers who have already purchased the product since signing up

For more on Klaviyo flows, see our guide to the 7 essential Klaviyo flows.

Step 4: Style the signup button

Klaviyo's default button styling is functional but basic. Customise the CSS to match your theme:

.klaviyo-bis-trigger button {
  width: 100%;
  padding: 1rem 2rem;
  background: #2D5A27;
  color: #fff;
  border: none;
  border-radius: 4px;
  font-size: 1rem;
  font-weight: 600;
  cursor: pointer;
  transition: background 0.2s;
}

.klaviyo-bis-trigger button:hover {
  background: #1e3d1a;
}

.klaviyo-bis-modal {
  /* Customise the modal popup */
  font-family: inherit;
}

.klaviyo-bis-modal input[type="email"] {
  width: 100%;
  padding: 0.75rem 1rem;
  border: 1px solid #ddd;
  border-radius: 4px;
  font-size: 1rem;
}

Option 2: Using a dedicated app

If you are not using Klaviyo, several Shopify apps provide back-in-stock functionality:

• Back in Stock — Restock Alerts by Appikon — free plan available, integrates with most email platforms
• Notify Me! Restock Alerts by Sajdoko — simple setup, good for smaller stores
• Stockbot — automated inventory tracking with notification features

The setup process for apps is typically:

1. Install the app from the Shopify App Store
2. Configure notification settings (email template, timing, branding)
3. The app automatically adds a notification button to sold-out products
4. Optionally customise the button placement and styling

The downside of app-based solutions is that they add JavaScript and HTTP requests to every product page, which can impact performance. We cover this in our app stack audit guide.

Option 3: Custom build

For stores that need full control over the experience, you can build back-in-stock notifications from scratch using Shopify's API, a database to store subscriber data, and an email service to send notifications.

Architecture overview

1. Frontend form — a signup form on the product page that captures the customer's email and the variant ID
2. Backend API — a serverless function or app that stores subscriptions in a database
3. Inventory webhook — listen to Shopify's inventory_levels/update webhook to detect restocks
4. Notification sender — when a restock is detected, query subscribers for that variant and send emails

// Simplified webhook handler for inventory updates
app.post('/webhooks/inventory-update', async (req, res) => {
  const { inventory_item_id, available } = req.body;

  // Check if item was previously out of stock and is now available
  if (available > 0) {
    const subscribers = await db.getSubscribers(inventory_item_id);

    for (const subscriber of subscribers) {
      await emailService.send({
        to: subscriber.email,
        template: 'back-in-stock',
        data: {
          productTitle: subscriber.productTitle,
          productUrl: subscriber.productUrl,
          productImage: subscriber.productImage,
          productPrice: subscriber.productPrice
        }
      });

      await db.markNotified(subscriber.id);
    }
  }

  res.status(200).send('OK');
});

This approach gives you complete control but requires ongoing maintenance. For most stores, Klaviyo or an app is the better choice unless you have specific requirements that cannot be met otherwise.

Designing the notification email

The notification email is critical — it needs to convert. Here are the elements that matter:

Subject line

Keep it simple and direct. Examples that work well:

• "Good news: [Product Name] is back in stock"
• "[Product Name] is available again — limited stock"
• "It's back! [Product Name] just restocked"

Email content

• Hero image — large, clear product image
• Product name and price — prominently displayed
• Urgency copy — "Limited stock available" or "This sold out fast last time"
• Single CTA button — "Shop Now" or "Buy Before It Sells Out"
• Direct link — link directly to the product page, not the homepage

Do not clutter the email with other products, navigation menus, or promotional content. This is a transactional-style email with one job: get the click.

Adding SMS notifications

SMS back-in-stock notifications are even more effective than email because they are seen within minutes. If you are using Klaviyo for SMS (available for UK brands), you can add an SMS step to your back-in-stock flow:

1. In the Klaviyo back-in-stock flow, add an SMS step alongside or instead of the email step
2. Keep the message short: "Great news! [Product] is back in stock. Grab yours before it sells out again: [link]"
3. Ensure you have SMS consent from the subscriber (GDPR and PECR compliant)
4. Add an SMS opt-in option to your back-in-stock signup form

For more on setting up SMS with Klaviyo, see our abandoned cart sequences guide which covers multi-channel notification strategies.

Optimising for conversions

Variant-level tracking

Track at the variant level, not just the product level. A customer who wanted the size M in blue does not want to be notified when size XL in red is restocked. Klaviyo supports variant-level tracking out of the box.

Timing matters

Send the notification immediately when stock is updated. Every hour of delay reduces conversion rates because:

• The customer may have found an alternative
• Other customers may buy the product before your subscriber gets the notification
• The urgency and excitement of availability diminishes with time

Create urgency

If the product sold out before, it will likely sell out again. Use honest urgency in your notification:

• Show remaining stock count if low ("Only 12 left")
• Reference the previous sellout ("This sold out in 48 hours last time")
• Set a time-limited early access window for notification subscribers

Follow up

Add a follow-up email 24-48 hours after the initial notification for subscribers who did not purchase. This captures customers who saw the first email but did not act immediately.

Common mistakes

1. Only tracking at product level

Customers want specific variants. Notifying someone that a product is back when their size is still sold out creates a poor experience and erodes trust.

2. Delayed notifications

Batching notifications or adding delays means your subscribers might arrive to find the product already sold out again. Send immediately.

3. No mobile optimisation

Over 70% of notification emails are opened on mobile. Ensure the product page they land on is mobile-optimised with a frictionless add-to-cart experience.

4. Ignoring the data

Back-in-stock signup data tells you which products have unmet demand. Share this data with your purchasing team to inform reorder quantities and timing.

5. Forgetting to remove the form

Ensure the "Notify me" button automatically disappears when the product comes back into stock. Showing both the notification form and the add-to-cart button is confusing.

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Back-in-stock notifications are one of the highest-ROI features you can add to a Shopify store. They recover revenue that would otherwise be lost, build your email list with high-intent subscribers, and provide valuable demand data for inventory planning.

If you are using Klaviyo, you can set this up in under an hour. If you need help integrating back-in-stock notifications into your Shopify store or Klaviyo setup, get in touch.