Run a fastify route with one command!

Usage no npm install needed!

<script type="module">
  import fastifyCli from '';



CI NPM version Known Vulnerabilities js-standard-style

Command line tools for Fastify. Generate, write, and run an application with one single command!


npm install fastify-cli --global


fastify-cli offers a single command line interface for your Fastify project:

$ fastify

Will print an help:

Fastify command line interface, available commands are:

  * start                 start a server
  * generate              generate a new project
  * generate-plugin       generate a new plugin project
  * readme                generate a for the plugin
  * print-routes          prints the representation of the internal radix tree used by the router, useful for debugging.
  * version               the current fastify-cli version
  * docs                  starts an interactive terminal session to view the Fastify docs for the Fastify version installed. navigate with arrow keys
  * help                  help about commands

Launch 'fastify help [command]' to know more about the commands.

The default command is start, you can hit

  fastify start plugin.js

to start plugin.js.


You can start any Fastify plugin with:

$ fastify start plugin.js

A plugin can be as simple as:

// plugin.js
module.exports = function (fastify, options, next) {
  fastify.get('/', function (req, reply) {
    reply.send({ hello: 'world' })

If you are using Node 8+, you can use Promises or async functions too:

// async-await-plugin.js
module.exports = async function (fastify, options) {
  fastify.get('/', async function (req, reply) {
    return { hello: 'world' }

For a list of available flags for fastify start see the help: fastify help start.

If you want to use custom options for the server creation, just export an options object with your route and run the cli command with the --options flag.

// plugin.js
module.exports = function (fastify, options, next) {
  fastify.get('/', function (req, reply) {
    reply.send({ hello: 'world' })

module.exports.options = {
  https: {
    key: 'key',
    cert: 'cert'

If you want to use custom options for your plugin, just add them after the -- terminator.

// plugin.js
module.exports = function (fastify, options, next) {
  if ( {
$ fastify start plugin.js -- --one

Modules in EcmaScript Module format can be used on Node.js >= 14 or >= 12.17.0 but < 13.0.0'

// plugin.js
export default async function plugin (fastify, options) {
  fastify.get('/', async function (req, reply) {
    return options

This works with a .js extension if you are using Node.js >= 14 and the nearest parent package.json has "type": "module" (more info here). If your package.json does not have "type": "module", use .mjs for the extension (plugin.mjs in the above example).


You can pass the following options via CLI arguments. Every option has a corresponding environment variable:

Description Short command Full command Environment variable
Port to listen on (default to 3000) -p --port FASTIFY_PORT or PORT
Address to listen on -a --address FASTIFY_ADDRESS
Socket to listen on -s --socket FASTIFY_SOCKET
Module to preload -r --require FASTIFY_REQUIRE
Log level (default to fatal) -l --log-level FASTIFY_LOG_LEVEL
Path to logging configuration module to use -L --logging-module FASTIFY_LOGGING_MODULE
Start Fastify app in debug mode with nodejs inspector -d --debug FASTIFY_DEBUG
Set the inspector port (default: 9320) -I --debug-port FASTIFY_DEBUG_PORT
Set the inspector host to listen on (default: loopback address or inside Docker) --debug-host FASTIFY_DEBUG_HOST
Prints pretty logs -P --pretty-logs FASTIFY_PRETTY_LOGS
Watch process.cwd() directory for changes, recursively; when that happens, the process will auto reload -w --watch FASTIFY_WATCH
Ignore changes to the specified files or directories when watch is enabled. (e.g. --ignore-watch='node_modules .git logs/error.log' ) --ignore-watch FASTIFY_IGNORE_WATCH
Prints events triggered by watch listener (useful to debug unexpected reload when using --watch ) --verbose-watch FASTIFY_VERBOSE_WATCH
Use custom options -o --options FASTIFY_OPTIONS
Set the prefix -x --prefix FASTIFY_PREFIX
Set the plugin timeout -T --plugin-timeout FASTIFY_PLUGIN_TIMEOUT
Defines the maximum payload, in bytes,
that the server is allowed to accept

By default fastify-cli runs dotenv, so it will load all the env variables stored in .env in your current working directory.

The default value for --plugin-timeout is 10 seconds. By default --ignore-watch flag is set to ignore `node_modules build dist .git bower_components logs .swp' files.


When deploying to a Docker, and potentially other, containers, it is advisable to set a fastify address of because these containers do not default to exposing mapped ports to localhost.

For containers built and run specifically by the Docker Daemon, fastify-cli is able to detect that the server process is running within a Docker container and the listen address is set automatically.

Other containerization tools (eg. Buildah and Podman) are not detected automatically, so the listen address must be set explicitly with either the --address flag or the FASTIFY_ADDRESS environment variable.

Fastify version discovery

If Fastify is installed as a project dependency (with npm install --save fastify), then fastify-cli will use that version of Fastify when running the server. Otherwise, fastify-cli will use the version of Fastify included within fastify-cli.

Migrating out of fastify-cli start

If you would like to turn your application into a standalone executable, just add the following server.js:

'use strict'

// Read the .env file.

// Require the framework
const Fastify = require('fastify')

// Require library to exit fastify process, gracefully (if possible)
const closeWithGrace = require('close-with-grace')

// Instantiate Fastify with some config
const app = Fastify({
  logger: true

// Register your application as a normal plugin.
const appService = require('./app.js')

// delay is the number of milliseconds for the graceful close to finish
const closeListeners = closeWithGrace({ delay: 500 }, async function ({ signal, err, manual }) {
  if (err) {
  await app.close()

app.addHook('onClose', async (instance, done) => {

// Start listening.
app.listen(process.env.PORT || 3000, (err) => {
  if (err) {

Unhandled rejections

fastify-cli uses make-promises-safe to avoid memory leaks in case of an 'unhandledRejection'.


fastify-cli can also help with generating some project scaffolding to kickstart the development of your next Fastify application. To use it:

  1. fastify generate <yourapp>
  2. cd yourapp
  3. npm install

The sample code offers you the following npm tasks:

  • npm start - starts the application
  • npm run dev - starts the application with pino-colada pretty logging (not suitable for production)
  • npm test - runs the tests

You will find three different folders:

  • plugins: the folder where you will place all your custom plugins
  • routes: the folder where you will declare all your endpoints
  • test: the folder where you will declare all your test

Finally, there will be an app.js file, which is your entry point. It is a standard Fastify plugin and you will not need to add the listen method to run the server, just run it with one of the scripts above.

If the target directory exists fastify generate will fail unless the target directory is ., as in the current directory.

If the target directory is the current directory (.) and it already contains a package.json file, fastify generate will fail. This can be overidden with the --integrate flag:

fastify generate . --integrate

This will add or alter the main, scripts, dependencies and devDependencies fields on the package.json. In cases of file name collisions for any files being added, the file will be overwritten with the new file added by fastify generate. If there is an existing app.js in this scenario, it will be overwritten. Use the --integrate flag with care.


Description Full command
Use the TypeScript template --lang=ts, --lang=typescript
Overwrite it when the target directory is the current directory (.) --integrate


fastify-cli can help you improve your plugin development by generating a scaffolding project:

  1. fastify generate-plugin <yourplugin>
  2. cd yourplugin
  3. npm install

The boilerplate provides some useful npm scripts:

  • npm run unit: runs all unit tests
  • npm run lint: to check your project's code style
  • npm run test:typescript: runs types tests
  • npm test: runs all the checks at once


fastify-cli can also help with generating a concise and informative readme for your plugin. If no package.json is provided a new one is generated automatically. To use it:

  1. cd yourplugin
  2. fastify readme <path-to-your-plugin-file>

Finally, there will be a new file, which provides internal information about your plugin e.g:

  • Install instructions
  • Example usage
  • Plugin dependencies
  • Exposed decorators
  • Encapsulation semantics
  • Compatible Fastify version


fastify-cli is unopinionated on the choice of linter. We recommend you to add a linter, like so:

"devDependencies": {
+ "standard": "^11.0.1",

"scripts": {
+ "pretest": "standard",
  "test": "tap test/**/*.test.js",
  "start": "fastify start -l info app.js",
  "dev": "fastify start -l info -P app.js",
+ "lint": "standard --fix"


fastify-cli allows you to view the documentation for Fastify in your terminal. By default, fastify-cli attempts to render the documentation for the Fastify version installed in the current working directory node_modules folder. However, if none are found it should fall back to rendering the documentation for the version that fastify-cli depends on.

The documentation is rendered using an interactive terminal session that you can navigate with your arrow keys and pressing the enter key to select documentation to view.

run fastify docs to get started.

Test helpers

When you use fastify-cli to run your project you need a way to load your application because you can run the CLI command. To do so, you can use the this module to load your application and give you the control to write your assertions. These utilities are async functions that you may use with the node-tap testing framework.

There are two utilities provided:

  • build: builds your application and returns the fastify instance without calling the listen method.
  • listen: starts your application and returns the fastify instance listening on the configured port.

Both of these utilities have the function(arg, pluginOptions) parameters:

  • cliArgs: is a string or a string array within the same arguments passed to the fastify-cli command.
  • pluginOptions: is an object containing the options provided to the started plugin (eg: app.js).
// load the utility helper functions
const { build, listen } = require('fastify-cli/helper')

// write a test
const { test } = require('tap')
test('test my application', async t => {
  const argv = ['app.js']
  const app = await build(argv, {
    extraParam: 'foo'
  t.teardown(() => app.close())
  // test your application here:
  const res = await app.inject('/')
  t.same(res.json(), { hello: 'one' })


If you feel you can help in any way, be it with examples, extra testing, or new features please open a pull request or open an issue.