Sign inDemoInstall


Package Overview
File Explorer

Advanced tools

Install Socket

Detect and block malicious and high-risk dependencies



Version published
Install size
13.4 MB




CI NPM version 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
  * eject                 turns your application into a standalone executable with a server.(js|ts) file being added
  * generate              generate a new project
  * generate-plugin       generate a new plugin project
  * generate-swagger      generate Swagger/OpenAPI schema for a project using @fastify/swagger
  * readme                generate a for the plugin
  * print-routes          prints the representation of the internal radix tree used by the router, useful for debugging.
  * print-plugins         prints the representation of the internal plugin tree used by avvio, useful for debugging.
  * version               the current fastify-cli version
  * 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. These options also get passed to your plugin via the options argument.

// 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'

And if you are using EcmaScript Module format:

export default async function plugin (fastify, options) {
  // Both `/foo` and `/foo/` are registered
  fastify.get('/foo/', async function (req, reply) {
    return 'foo'

export const options = {
  ignoreTrailingSlash: true

If you want to use custom options for your plugin, just add them after the -- terminator. If used in conjunction with the --options argument, the CLI arguments take precedence.

// 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. You can also use --config or -c flag to pass a configuration file that exports all the properties listed below in camelCase convention. In case of collision (i.e., An argument existing in both the configuration file and as a command-line argument, the command-line argument is given the priority). Every option has a corresponding environment variable:

DescriptionShort commandFull commandEnvironment variable
Path to configuration file that can be used to manage the options listed below-c--configFASTIFY_CONFIG or CONFIG
Port to listen on (default to 3000)-p--portFASTIFY_PORT or PORT
Address to listen on-a--addressFASTIFY_ADDRESS
Socket to listen on-s--socketFASTIFY_SOCKET
Module to preload-r--requireFASTIFY_REQUIRE
ES Module to preload-i--importFASTIFY_IMPORT
Log level (default to fatal)-l--log-levelFASTIFY_LOG_LEVEL
Path to logging configuration module to use-L--logging-moduleFASTIFY_LOGGING_MODULE
Start Fastify app in debug mode with nodejs inspector-d--debugFASTIFY_DEBUG
Set the inspector port (default: 9320)-I--debug-portFASTIFY_DEBUG_PORT
Set the inspector host to listen on (default: loopback address or inside Docker or Kubernetes)--debug-hostFASTIFY_DEBUG_HOST
Prints pretty logs-P--pretty-logsFASTIFY_PRETTY_LOGS
Watch process.cwd() directory for changes, recursively; when that happens, the process will auto reload-w--watchFASTIFY_WATCH
Ignore changes to the specified files or directories when watch is enabled. (e.g. --ignore-watch='node_modules .git logs/error.log' )--ignore-watchFASTIFY_IGNORE_WATCH
Prints events triggered by watch listener (useful to debug unexpected reload when using --watch )-V--verbose-watchFASTIFY_VERBOSE_WATCH
Use custom options-o--optionsFASTIFY_OPTIONS
Set the prefix-x--prefixFASTIFY_PREFIX
Set the plugin timeout-T--plugin-timeoutFASTIFY_PLUGIN_TIMEOUT
Defines the maximum payload, in bytes,
that the server is allowed to accept
Set the maximum ms delay before forcefully closing pending requests after receiving SIGTERM or SIGINT signals; and uncaughtException or unhandledRejection errors (default: 500)-g--close-grace-delayFASTIFY_CLOSE_GRACE_DELAY

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 container, 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 or inside a Kubernetes cluster, fastify-cli is able to detect that the server process is running within a 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
closeWithGrace({ delay: process.env.FASTIFY_CLOSE_GRACE_DELAY || 500 }, async function ({ signal, err, manual }) {
  if (err) {
  await app.close()

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


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-pretty pretty logging (not suitable for production)
  • npm test - runs the tests
  • npm run lint - fixes files accordingly to linter rules, for templates generated with --standardlint

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.

DescriptionFull command
To generate ESM based JavaScript template--esm
Use the TypeScript template--lang=ts, --lang=typescript
Overwrite it when the target directory is the current directory (.)--integrate
For JavaScript template, optionally includes Standard linter to fix code style issues--standardlint


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


if your project uses @fastify/swagger, fastify-cli can generate and write out the resulting Swagger/OpenAPI schema for you.

fastify generate-swagger app.js


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"

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(args, pluginOptions, serverOptions) parameters:

  • args: 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).
  • serverOptions: is an object containing the additional options provided to fastify server, similar to the --options command line argument
// 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' })

Log output is consumed by tap. If log messages should be logged to the console the logger needs to be configured to output to stderr instead of stdout.

const logger = {
  transport: {
    target: 'pino-pretty',
    options: {
      destination: 2,
const argv = ['app.js']
test('test my application with logging enabled', async t => {
  const app = await build(argv, {}, { logger })
  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.

How to execute the CLI

Instead of using the fastify keyword before each command, use node cli.js
Example: replace fastify start with node cli.js start





Last updated on 12 Jun 2024

Did you know?


Socket for GitHub automatically highlights issues in each pull request and monitors the health of all your open source dependencies. Discover the contents of your packages and block harmful activity before you install or update your dependencies.


Related posts

SocketSocket SOC 2 Logo


  • Package Alerts
  • Integrations
  • Docs
  • Pricing
  • FAQ
  • Roadmap


Stay in touch

Get open source security insights delivered straight into your inbox.

  • Terms
  • Privacy
  • Security

Made with ⚡️ by Socket Inc