What's the best way to save cart contents for returning visitors?

As an e-commerce store owner, cart abandonment is my constant nightmare. I've watched countless potential sales slip away because customers get distracted, leave, and then can't remember what they were about to purchase. It's incredibly frustrating to see traffic and potential revenue just vanish. I've tried multiple approaches - browser cookies, local storage, even manual email reminders - but nothing seems consistent or reliable. My conversion rates suffer because customers have to start over, which creates unnecessary friction. Every time a customer has to re-add items, I'm essentially asking them to make a purchase decision all over again. This isn't just about convenience; it's about creating a smooth, frictionless shopping experience that respects my customers' time and keeps their purchase intent intact. I need a solution that automatically preserves cart contents, works across devices, and doesn't rely on customers having an account. It should feel seamless, secure, and intelligent - almost like the cart is waiting patiently for them, ready to pick up exactly where they left off.