inlets combines a reverse proxy and websocket tunnels to expose your internal and development endpoints to the public Internet via an exit-node. An exit-node may be a 5-10 USD VPS or any other computer with an IPv4 IP address.
You may be wondering why this project needs to exist, since many like it have come before. The author addresses that right up front:
Similar tools such as ngrok or Argo Tunnel from Cloudflare are closed-source, have limits built-in, can work out expensive and have limited support for arm/arm64. Ngrok is also often banned by corporate firewall policies meaning it can be unusable. Other open-source tunnel tools are designed to only set up a static tunnel. inlets aims to dynamically bind and discover your local services to DNS entries with automated TLS certificates to a public IP address over its websocket tunnel.