How to Add a Custom “Back in Stock Notification” System in WooCommerce Using Hooks

Out-of-stock products don’t have to mean lost sales.
With a back-in-stock notification system, you can collect customer interest and bring them back when the product becomes available again.

In this tutorial, you will learn how to create a simple back-in-stock notification system using WooCommerce hooks.

Why This Feature Is Powerful

Instead of losing customers when a product is unavailable, you keep them engaged and ready to buy later.

• Recovers lost sales opportunities
• Builds email list automatically
• Improves customer retention
• Increases future conversions

The WooCommerce Hook We Will Use

We will use:

woocommerce_single_product_summary

This hook allows us to show a custom form on the product page.

Step 1: Show Notification Form

Add this code to your theme’s functions.php file or a custom plugin:

add_action('woocommerce_single_product_summary', 'back_in_stock_form', 30);

function back_in_stock_form() {

    global $product;

    if (!$product || $product->is_in_stock()) {
        return;
    }

    echo '
';
    echo '
This product is currently out of stock.
';
    echo '
Get notified when it becomes available again:
';

    echo '
';
    echo '';
    echo 'Notify Me';
    echo '
';

    echo '
';
}

Step 2: Handle Form Submission

Now we capture the email submission:

add_action('init', 'handle_back_in_stock_submission');

function handle_back_in_stock_submission() {

    if (!isset($_POST['restock_email'])) {
        return;
    }

    $email = sanitize_email($_POST['restock_email']);

    if (!is_email($email)) {
        return;
    }

    // Here you can store email in database or send to CRM
    update_option('restock_request_' . time(), $email);
}

How It Works

• Checks if product is out of stock
• Displays email subscription form
• Saves user email when submitted

Advanced Improvements

• Store emails per product ID
• Send automatic email when product restocks
• Integrate with Mailchimp or CRM
• Add double opt-in confirmation