2.0.1 • Public • Published


spio exposes your localhost to the world for easy testing and sharing! No need to mess with DNS or deploy just to have others test out your changes.

Great for working with browser testing tools like browserling or external api callback services like twilio which require a public url for callbacks.



npm i -g spio

As a dependency in your project

npm i spio

CLI usage

When spio is installed globally, just use the spio command to start the tunnel.

spio --port 8000

Thats it! It will connect to the tunnel server, setup the tunnel, and tell you what url to use for your testing. This url will remain active for the duration of your session; so feel free to share it with others for happy fun time!

You can restart your local server all you want, spio is smart enough to detect this and reconnect once it is back.


Below are some common arguments. See spio --help for additional arguments

  • --subdomain request a named subdomain on the spio server (default is random characters)
  • --local-host proxy to a hostname other than localhost

You may also specify arguments via env variables. E.x.

PORT=3000 spio


The spio client is also usable through an API (for test integration, automation, etc)

spio(port [,options][,callback])

Creates a new spio to the specified local port. Will return a Promise that resolves once you have been assigned a public spio url. options can be used to request a specific subdomain. A callback function can be passed, in which case it won't return a Promise. This exists for backwards compatibility with the old Node-style callback API. You may also pass a single options object with port as a property.

const spio = require('spio');
(async () => {
  const tunnel = await spio({ port: 3000 });
  // the assigned public url for your tunnel
  // i.e. http://something-subdomain.spiderium.xyz
  tunnel.on('close', () => {
    // tunnels are closed


  • port (number) [required] The local port number to expose through spio.
  • subdomain (string) Request a specific subdomain on the proxy server. Note You may not actually receive this name depending on availability.
  • host (string) URL for the upstream proxy server. Defaults to http://spiderium.xyz.
  • local_host (string) Proxy to this hostname instead of localhost. This will also cause the Host header to be re-written to this value in proxied requests.
  • local_https (boolean) Enable tunneling to local HTTPS server.
  • local_cert (string) Path to certificate PEM file for local HTTPS server.
  • local_key (string) Path to certificate key file for local HTTPS server.
  • local_ca (string) Path to certificate authority file for self-signed certificates.
  • allow_invalid_cert (boolean) Disable certificate checks for your local HTTPS server (ignore cert/key/ca options).

Refer to tls.createSecureContext for details on the certificate options.


The tunnel instance returned to your callback emits the following events

event args description
request info fires when a request is processed by the tunnel, contains method and path fields
error err fires when an error happens on the tunnel
close fires when the tunnel has closed

The tunnel instance has the following methods

method args description
close close the tunnel




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