Free SSL and managed or automatic HTTPS for node.js with Express, Koa, Connect, Hapi, and all other middleware systems.

Usage no npm install needed!

<script type="module">
  import saltcornGreenlockExpress from 'https://cdn.skypack.dev/@saltcorn/greenlock-express';


Greenlock Express v4 is Let's Encrypt for Node

| Built by Root for Hub |

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Free SSL for Node Web Servers

Greenlock Express is a Web Server with Fully Automated HTTPS and renewals.

You define your app and let Greenlock handle issuing and renewing Free SSL Certificates.

npm init
npm install --save greenlock-express@v4


"use strict";

var app = require("./app.js");

        packageRoot: __dirname,
        configDir: "./greenlock.d",

        // contact for security and critical bug notices
        maintainerEmail: "jon@example.com",

        // whether or not to run at cloudscale
        cluster: false
    // Serves on 80 and 443
    // Get's SSL certificates magically!


{ "sites": [{ "subject": "example.com", "altnames": ["example.com"] }] }

Let's Encrypt for...

  • IoT
  • Enterprise On-Prem
  • Local Development
  • Home Servers
  • Quitting Heroku


  • Let's Encrypt v2 (November 2019)
    • ACME Protocol (RFC 8555)
    • HTTP Validation (HTTP-01)
    • DNS Validation (DNS-01)
    • ALPN Validation (TLS-ALPN-01)
  • Automated HTTPS
    • Fully Automatic Renewals every 45 days
    • Free SSL
    • Wildcard SSL
    • Localhost certificates
    • HTTPS-enabled Secure WebSockets (wss://)
    • Cloud-ready with Node cluster.
  • Fully customizable
    • Reasonable defaults
    • Domain Management
    • Key and Certificate Management
    • ACME Challenge Plugins


Works with any node http app, including

  • Express
  • Koa
  • hapi
  • rill
  • http2
  • cluster
  • etc...

v4 QuickStart

Serving sites with Free SSL is as easy as 1, 2, 3... 4


  1. Create a Project with Greenlock Express
    • server.js
    • app.js
  2. Setup the config file (or database)
    • .greenlockrc
    • greenlock.d/config.json
  3. Add Domains
    • npx greenlock add --subject example.com --altnames example.com
  4. Hello, World!
    • npm start -- --staging


If you're familiar with node, npm, and npx: this is all you need to do:

npm init
npm install --save greenlock-express@v4

npx greenlock init --config-dir greenlock.d --maintainer-email jon@example.com
npx greenlock add --subject example.com --altnames example.com

npm start -- --staging

Once you've tested that that works, you can change app.js to suit your needs replace the built-in callbacks for things like certificate storage as you like.

1. Create your Project

If you need to install Node.js, do so:

Mac, Linux:

curl -fsS https://webinstall.dev/node | bash

Windows 10:

curl -fsSA "MS" https://webinstall.dev/node | powershell

Then create a directory for your project, and initialize it:

mkdir -p my-sites
pushd my-sites
npm init
npm install --save greenlock-express@v4

2. Initialize and Config (Dir or DB)

You can use local file storage or a database. The default is to use file storage.

You'll need to create server.js and greenlock.d/config.json. You can do so using the CLI, API, or by hand.

Using the CLI (simplest, recommended)

Anytime you install an npm module that contains an executable, you can run it using npx.

To initialize the Greenlock config, run npx greenlock init:

npx greenlock init --config-dir ./greenlock.d --maintainer-email 'jon@example.com'

By Hand (for advanced users)

Create server.js like so:


'use strict';

var app = require('./app.js');

        packageRoot: __dirname,

        // where to look for configuration
        configDir: './greenlock.d',

        // whether or not to run at cloudscale
        cluster: false
    // Serves on 80 and 443
    // Get's SSL certificates magically!

Create app.js like so:


'use strict';

// Here's a vanilla HTTP app to start,
// but feel free to replace it with Express, Koa, etc
var app = function(req, res) {
    res.end('Hello, Encrypted World!');

module.exports = app;

Greenlock uses .greenlockrc to figure out whether to use the file system or a database for config, as well as where its root directory is.



The greenlock.d/config.json is NOT intended to be edited by hand, as it is a substitute for a database, but it looks like this:

{ "defaults": { "subscriberEmail": "john.doe@example.com" }, "sites": [] }

3. Add Sites

For security, you must specify which sites you allow to request certificates. If you need this to be dynamic (i.e. checking a database or API, see the section below on custom site managers).

Every site has a "subject" (its primary domain name) and one or more "altnames" (secondary or related domain names on the same certificate).

Using CLI (simple, recommended)

Simply supply the names of sites that you manage and they will be added to the file system config, or database.

npx greenlock add --subject example.com --altnames example.com,www.example.com

By Hand (debugging only)

You should NOT edit greenlock.d/config.json with your own tools. Use greenlock.manager.add({}) instead.


{ "sites": [{ "subject": "example.com", "altnames": [ "example.com", "www.example.com" ] }] }

4. Hello, Encrypted World!

That was it! Now you can run your server!

When you run npm start, it will automatically run node server.js (or package.json.scripts.start).

For arguments that npm start should ignore, place them after --.

Here we use --staging in order to tell greenlock to issue test certificates rather than real certificates.

# Note: you can use npm start to run server.js with the --staging flag set
npm start -- --staging
> my-project@1.0.0 start /srv/www/my-project
> node server.js

Listening on for ACME challenges and HTTPS redirects
Listening on for secure traffic

If everything worked you can visit your site in your browser, and after a few seconds you'll get a certificate warning and, after that, see a "Hello World" message. The debug (staging) certificates will be saved in greenlock.d/staging. Run again without --staging and you will get real certificates.

Season to taste

Now you're ready to update app.js with your code. For example, try this next:

npm install --save express
mkdir -p public
echo '<h1>Hello!</h1>' >> public/index.html


'use strict';

var path = require('path');
var express = require('express');
var app = express();

app.get('/', express.static(path.join(__dirname, "public")));

module.exports = app;

// for development and debugging
if (require.main === module) {
    require('http').createServer(app).listen(3000, function () {
        console.info("Listening for HTTP on", this.address());


For a more detail read the full WALKTHROUGH.


To see all of the examples, just browse greenlock-express.js/examples/

Example Location + Description
Express ./examples/express/ how to export an express app
Node's http2 ./examples/http2/ how to use Node's built-in http2 server
Node's https ./examples/https how to customize the https server
WebSockets ./examples/websockets/ how to use on('upgrade')
Socket.IO ./examples/socket.io how to overcomplicate a persistent connection
Cluster ./examples/cluster/ how to use Node's built-in clustering with master and worker processes
Wildcards coming someday (ask to help create this) how to use DNS-01 for wildcard certs
Localhost coming someday (ask to help create this) how to use DNS-01 for domains that resolve to private networks, such as
CI/CD coming someday (ask to help create this) how to use the --staging environment for test deployments
HTTP Proxy examples/http-proxy how to (reverse) proxy decrypted traffic to another server
- Build your own
Be sure to tell me about it (open an issue)


1. But did YOU read the QuickStart?

99% of the questions I get are answered in the QuickStart, or in the Examples.

Before you go into your specific use case, just try out the QuickStart from start to finish so that you can see that the default setup works, you get feel for the "lay of the land", and you know what to edit.

2. How to use JavaScript configuration?

You don't. It's JSON on purpose.

The configuration has to be serializable (i.e. could go in a database).

The config file is meant for simple use cases, for the average dev and it is managed with npx greenlock ..., as shown in the QuickStart.

If you have a dynamic or advanced use case (i.e. you need stuff in a database, or to change config on-the-fly), you can use the Greenlock API (not Greenlock Express) and you'll love it.

If you're layering a lot of complexity with dev ops tools, but you don't really understand the tools that well (i.e. Docker), either use ENVIRONMENT variables or put the npx greenlock ... commands in your setup script. You MUST use a database for lambda "cloud functions" and such.

You can also just mangle the Greenlock API to do what you want... but I don't recommend it. Keep it simple and your future self with thank you.

General rule of thumb: commit code, not data / config.

3. How to use non-standard ports (not 80, 443)?

You don't. Not usually.

Let's Encrypt REQUIRES port 80 for HTTP-01 challenges.

But if you're using DNS-01 or you have a proxy in place, just use the raw node server. See these examples:

If you want to use Greenlock as a proxy, see this example:


What if the example didn't work?

Double check the following:

  • Public Facing IP for http-01 challenges
    • Are you running this as a public-facing webserver (good)? or localhost (bad)?
    • Does ifconfig show a public address (good)? or a private one - 10.x, 192.168.x, etc (bad)?
    • If you're on a non-public server, are you using the dns-01 challenge?
  • valid email
    • You MUST set maintainerEmail to a valid address
    • MX records must validate (dig MX example.com for 'john@example.com')
  • valid DNS records
    • Must have public DNS records (test with dig +trace A example.com; dig +trace www.example.com for [ 'example.com', 'www.example.com' ])
  • write access
    • You MUST set configDir to a writeable location (test with touch ./greenlock.d/config.json)
  • port binding privileges
    • You MUST be able to bind to ports 80 and 443
    • You can do this via sudo or setcap
  • API limits
    • You MUST NOT exceed the API usage limits per domain, certificate, IP address, etc
  • Red Lock, Untrusted
    • You MUST switch from npm start -- --staging to npm start to use the production server
    • The API URL should not have 'acme-staging-v02', but should have 'acme-v02'

Using a Database, S3, etc

If you have a small site, the default file storage will work well for you.

If you have many sites with many users, you'll probably want to store config in a database of some sort.

See the section on Custom callbacks and plugins below.

Advanced Configuration

All of the advanced configuration is done by replacing the default behavior with callbacks.

You can whip up your own, or you can use something that's published to npm.

See the section on Custom callbacks and plugins below.

Easy to Customize

  • Custom Domain Management
    • edit server.js and/or .greenlockrc to switch from the default configDir manager to your config system or database
    • CLI example: npx greenlock init --manager ./path-or-npm-name.js --manager-FOO 'set option FOO'
  • Custom Key & Cert Storage
    • edit the defaults section of greenlock.d/config.json to change the certificate store or database
    • CLI example: npx greenlock defaults --store greenlock-store-fs --store-base-path ./greenlock.d
  • Custom ACME HTTP-01 Challenges
    • edit the defaults section of greenlock.d/config.json to change the challenges by hand
    • CLI example: npx greenlock defaults --challenge-http-01 ./you-http-01.js
  • Custom ACME DNS-01 Challenges
    • edit the defaults section of greenlock.d/config.json to change the challenges by hand
    • CLI example: npx greenlock defaults --challenge-dns-01 acme-dns-01-ovh --challenge-dns-01-token xxxx
    • Per-site example: npx greenlock update --subject example.com --challenge-dns-01 ./your-dns-01.js
    • API example:
          subject: "example.com",
          challenges: {
              "dns-01": {
                  module: "my-npm-module-name",
                  foo: "some option",
                  bar: "some other option"

If you're using the default configDir management you can edit greenlock.d/config.json by hand to change which default and per-site modules are used.

You can use the CLI, even if you're using a database, buckets, or your own file storage.

You can also use the API, particularly if you need to set values dynamically per-site or per-user rather than using the global defaults. The certificate store and all challenges can be set per-site, but most per-site use cases are for DNS-01.

Ready-made Integrations

Greenlock Express integrates between Let's Encrypt's ACME Challenges and many popular services.

Type Service Plugin
dns-01 CloudFlare acme-dns-01-cloudflare
dns-01 Digital Ocean acme-dns-01-digitalocean
dns-01 DNSimple acme-dns-01-dnsimple
dns-01 DuckDNS acme-dns-01-duckdns
http-01 File System / Web Root acme-http-01-webroot
dns-01 GoDaddy acme-dns-01-godaddy
dns-01 Gandi acme-dns-01-gandi
dns-01 NameCheap acme-dns-01-namecheap
dns-01 Name.com acme-dns-01-namedotcom
dns-01 Route53 (AWS) acme-dns-01-route53
http-01 S3 (AWS, Digital Ocean, Scaleway) acme-http-01-s3
dns-01 Vultr acme-dns-01-vultr
dns-01 Build your own acme-dns-01-test
http-01 Build your own acme-http-01-test
tls-alpn-01 Contact us -

Example Usage:

npx greenlock defaults --challenge-dns-01 acme-dns-01-ovh --challenge-dns-01-token xxxx
npx greenlock defaults --challenge-http-01 acme-http-01-s3 --challenge-http-01-bucket my-bucket

Search acme-http-01- or acme-dns-01- on npm to find more.

Full Documentation

Most of the documentation is done by use-case examples, as shown up at the top of the README.

We're working on more comprehensive documentation for this newly released version. Please open an issue with questions in the meantime.

Commercial Support

Do you need...

  • training?
  • specific features?
  • different integrations?
  • bugfixes, on your timeline?
  • custom code, built by experts?
  • commercial support and licensing?

You're welcome to contact us in regards to IoT, On-Prem, Enterprise, and Internal installations, integrations, and deployments.

We have both commercial support and commercial licensing available.

We also offer consulting for all-things-ACME and Let's Encrypt.

Legal & Rules of the Road

Greenlock™ is a trademark of AJ ONeal

The rule of thumb is "attribute, but don't confuse". For example:

Built with Greenlock Express (a Root project).

Please contact us if you have any questions in regards to our trademark, attribution, and/or visible source policies. We want to build great software and a great community.

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