Add back-in-stock email notifications to WooCommerce: a plugin you can build today

WooCommerce handles stock tracking for the store owner. You can set quantities per product, enable low-stock warnings at a configurable threshold, and have stock update automatically when orders are placed. The product list in the admin shows current levels across your catalogue and flags anything that needs attention.

The customer-facing side covers display only. WooCommerce shows an out-of-stock badge and can hide unavailable products from shop archives if you prefer. It does not offer customers a way to register interest or receive a notification when a product returns.

The WooCommerce extension library includes a paid Waitlist plugin from WooCommerce itself, as well as third-party options such as Back In Stock Notifier for WooCommerce and YITH WooCommerce Waiting List. These add sign-up forms, subscriber management, and automated emails. The plugin in this guide covers the same core need for stores that want a single-file build without a recurring cost.

Abandoned cart email requires session tracking, cart-level data, and a delay timer configured carefully enough that it does not fire on normal session drops. The customer also has to reach the cart before the sequence begins. For stores where products go out of stock regularly, back-in-stock reaches an earlier and more motivated group.

The trigger for back-in-stock is an event you control: updating the stock status. The subscriber list is self-selected; every address on it belongs to a customer who said they want that specific product. The email is short, factual, and expected. The sequence is deterministic, which makes testing it easier than any time-delayed automation.

The waiting list also gives you a lightweight demand signal. A product with forty subscribers is worth restocking before something with two. The admin table shows subscriber count per product and the date of the most recent signup, which is enough to prioritise a restock decision without additional tooling.

The plugin registers a shortcode [wc_back_in_stock_form] that renders an email input and a submit button. You paste it into the product description, add it to a template file, or output it via a hook in your theme. The form submits to the same page and validates the email address before inserting a row into a custom database table. If the same email is already on the list for that product, the plugin shows a notice and does not create a duplicate.

When you save a product with its stock status set to in stock, the plugin intercepts the woocommerce_product_set_stock_status action. It queries the subscriber table for that product. If any subscribers exist, it sends each a plain-text email via wp_mail with the product name in the subject and a link to the product in the body, then deletes all subscriber records for that product. If the product goes out of stock again and new customers sign up, they will be notified on the next restock.

The admin page at WooCommerce > Back In Stock shows a grouped summary: product name as a link, subscriber count, and date of the most recent signup, ordered by count descending. There is no per-subscriber view, individual email lookup, or export in the initial build.

Variable products are tracked at the parent product level. If you sell a shirt in three sizes and only one size goes out of stock, customers who sign up via the parent product page are subscribed to the parent. Notification fires when the parent stock status changes to in stock, which may not match the moment a specific variation the customer wanted returns. Stores with variation-heavy catalogues need a dedicated plugin that tracks subscriptions at the variation level.

Notifications are sent synchronously in the same request that triggers the stock status change. For a product with a handful of subscribers this is fine. For a product with hundreds of waiting customers, the admin save request will be slow and could time out on shared hosting. If you expect large waiting lists, a plugin with queue-based email sending is the better tool.

There is no double opt-in. A customer who enters an email address is added immediately without a confirmation step. The follow-up prompt at the end of this guide adds a signed-token confirmation email if that matters for your legal environment or email list hygiene.

The plugin does not connect to Klaviyo, Brevo, Mailchimp, or any other email platform. All email goes through wp_mail using your site's configured mail transport. Without an SMTP plugin, deliverability will be poor and notifications may land in spam. Configure a transactional mail service before relying on this for customer-facing email.

If products regularly sell out and you expect waiting lists of more than a few dozen at a time, a plugin with background email sending is the right choice. Back In Stock Notifier for WooCommerce and YITH WooCommerce Waiting List both handle volume through queued sending rather than processing everything in the admin save request.

If you need variation-level waiting lists, subscriber export, or direct integration with your email marketing platform, those features do not exist in the initial build here. This plugin suits stores where out-of-stock events are occasional, lists stay small, and the goal is to capture demand without adding a recurring fee.

Paste the prompt below into Steem to build the plugin. To add double opt-in and an unsubscribe link, the follow-up is: 'Add double opt-in to WC Back In Stock: when the form is submitted, send a confirmation email with a signed URL containing a token. Only insert the subscriber row when the token link is clicked. Include an unsubscribe link in the stock notification email that removes the subscriber record via a second signed token URL.'