$ npm start
Error: listen EADDRINUSE: address already in use :::3000

Eliminate port conflicts in your dev environment.

Port Zero lets the OS pick random available ports, then forwards them to virtual domains on a virtual NIC. Run multiple branches simultaneously without clashing.

Download How It Works
Install

Up in seconds

Pick your platform. The daemon starts automatically on login.

$ brew install PortZeroNetwork/portzero/port-zero
How It Works

Configure ports to 0. Set one env var.

Port Zero's daemon watches for processes with PZ_TUNNEL and routes traffic automatically. The domain you choose determines the scope.

Local — free
# resolves on your machine and LAN
PZ_TUNNEL=main.myapp.portzero.local:80 npm start
# http://main.myapp.portzero.local:80 is now live
Cloud — subscription
# reachable anywhere on the internet
PZ_TUNNEL=main.myapp.portzero.cloud:80 npm start
# https://main.myapp.portzero.cloud is now live
1

Set ports to 0

Configure every service to bind on port 0. The OS picks a free port at random — conflicts are structurally impossible.

2

Set PZ_TUNNEL

Use portzero.local for on-machine routing or portzero.cloud for internet tunnels. Same syntax either way.

3

Start your app

The daemon finds the process, assigns it a stable address, and starts routing. Your app code doesn't change at all.

Features

Built for real development workflows

Every feature follows from one idea: ports should never be your problem.

Multiple branches simultaneously

Running main and feature-auth in separate worktrees? Each gets its own address. Both live at once — no restarts, no juggling.

http://main.myapp.portzero.local:80
http://feature-auth.myapp.portzero.local:80

Any TCP protocol

Not just HTTP. WebSockets, gRPC, raw TCP, database connections — Port Zero routes it all. If it runs over TCP, it works.

Internet tunnels, no config

Switch portzero.local to portzero.cloud and your service is on a public HTTPS URL. No firewall rules, no reverse proxy setup.

Stable, predictable addresses

Every service gets the same address every run. Share a URL with a teammate — it still works tomorrow. No random subdomains, no re-auth.

Under the Hood

What actually happens

A daemon runs on your machine and watches for PZ_TUNNEL. The domain determines which path it takes.

Local path (portzero.local)

  1. 1 Creates a virtual NIC on your machine (once, on first run).
  2. 2 Assigns the service a unique virtual IP on that NIC.
  3. 3 Creates a DNS record for that IP using the PZ_TUNNEL template.
  4. 4 Forwards the virtual IP's port to the actual (random) port your process bound to.

Cloud path (portzero.cloud)

  1. 1 Daemon detects portzero.cloud in PZ_TUNNEL.
  2. 2 Opens an outbound tunnel to our edge servers — no inbound ports needed.
  3. 3 Traffic to your subdomain is proxied back through the tunnel to your local service over TLS.
Pricing

Simple, transparent pricing

Local routing is always free. Pay only for cloud tunnels.

Free
$0/mo

Local routing + one cloud tunnel to try it

  • Unlimited local routing
  • 1 cloud tunnel
  • 50 requests/day
  • 50 MB/day
  • Community support
Get Started Free
Most Popular
Pro
$2/mo

For developers who share work daily

  • Unlimited local routing
  • 10 cloud tunnels
  • 10,000 requests/day
  • 350 MB/day
  • Priority support
Get Started
Contact

Send us a message

Questions, bug reports, partnership notes, or anything else.

Tell us what you need

Include context, links, or a tunnel domain if that helps. We reply by email.

  • Product questions and feature requests
  • Billing, account, and login issues
  • Partnerships, press, and general support

Prefer email? Write to support@portzero.net.