Back In Stock Notifications (WooCommerce Extension) lets both logged-in customers and guest users subscribe to receive an email when out-of-stock products (including variations) are restocked.

On product pages that show “Out of stock,” the plugin adds a sign-up form (or waitlist) so customers can register interest. Once stock is restored, the plugin queues notification emails and sends them in batches via WooCommerce’s Action Scheduler, helping to manage large volumes without performance issues.