localtunnel — Expose Your Localhost to the World Instantly

Introduction

localtunnel provides a public HTTPS URL that forwards to a port on your local machine. It is especially useful for testing webhooks, sharing in-progress work with teammates, and running quick demos without deploying to a server.

What localtunnel Does

• Creates an HTTPS tunnel from a public URL to a local port in one command
• Supports custom subdomains so you can get a predictable URL
• Works behind NATs and corporate firewalls without router configuration
• Runs as a CLI tool or can be used programmatically via its Node.js API
• Allows self-hosting the tunnel server for teams that need a private relay

Architecture Overview

localtunnel opens a connection to a remote relay server that listens for incoming HTTPS requests on a generated subdomain. When a request arrives, the server multiplexes it over the existing connection back to the client, which forwards it to the local port. The client maintains a pool of sockets to the relay for concurrent request handling.

Self-Hosting & Configuration

• Install globally with npm install -g localtunnel or run via npx
• Self-host the server component using localtunnel-server for private relays
• Set a custom subdomain with --subdomain myname for a stable URL
• Configure the local host with --local-host 192.168.1.x if not localhost
• Supports --print-requests flag to log incoming request details

Key Features

• Zero-config tunneling with a single CLI command
• Free public relay at loca.lt with HTTPS included
• Custom subdomains for stable, bookmarkable URLs
• Programmatic API for integration into build scripts and test runners
• Open-source server for self-hosting a private tunnel relay

Comparison with Similar Tools

• ngrok — Feature-rich commercial tunnel with a generous free tier; localtunnel is simpler and fully open-source
• Cloudflare Tunnel — Requires a Cloudflare account; localtunnel needs no sign-up
• Tailscale Funnel — Mesh VPN approach; localtunnel is a lighter single-purpose tool
• bore — Minimal Rust tunnel; localtunnel adds subdomain support and a Node.js API

FAQ

Q: Is the public loca.lt relay free to use? A: Yes. The default relay is free with no sign-up, though it may have rate limits for heavy traffic.

Q: Can I use localtunnel for production traffic? A: It is designed for development and demos. For production, self-host the server or use a dedicated tunnel service.

Q: Does it support TCP or only HTTP? A: localtunnel is HTTP/HTTPS only. For raw TCP tunnels, consider tools like chisel or bore.

Q: How do I get a consistent URL between restarts? A: Use the --subdomain flag to request the same subdomain each time, for example lt --port 3000 --subdomain myapp.

Sources

• https://github.com/localtunnel/localtunnel
• https://theboroer.github.io/localtunnel-www/