ngrok HLD: Exposing localhost to the Internet With Reverse Tunnels

Your app is running on localhost:3000 and Stripe needs to POST a webhook to it — right now, from their servers to your laptop. But your machine has no public IP, sits behind your router's NAT, and your office firewall won't let you open an inbound port even if you asked. Every obvious fix (port-forward, a static IP, a VPN) is a config battle you'll lose. ngrok solves it with one inversion that sounds backwards until it clicks: instead of the world reaching in to you, your machine dials out to a public edge server and holds that one connection open — and the edge then pushes Stripe's inbound re…