Every out-of-stock product is a customer about to leave forever. Amp: Back in Stock & PreOrder+ captures them with a "Notify Me" button, builds a waitlist, and auto-fires alerts the moment you restock - via email, SMS, or push. Pre-sell upcoming drops and collect revenue before inventory lands. Wishlists and low-stock alerts let you capture intent at every stage. Built for high-SKU catalogs. Set up in minutes. Hundreds of millions of alerts delivered across 25,000+ brands since 2011.