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CI Package Manager CI Web SIte js-standard-style CII Best Practices

NPM version NPM downloads Security Responsible Disclosure Discord

An efficient server implies a lower cost of the infrastructure, a better responsiveness under load and happy users. How can you efficiently handle the resources of your server, knowing that you are serving the highest number of requests as possible, without sacrificing security validations and handy development?

Enter Fastify. Fastify is a web framework highly focused on providing the best developer experience with the least overhead and a powerful plugin architecture. It is inspired by Hapi and Express and as far as we know, it is one of the fastest web frameworks in town.

The main branch refers to the Fastify v4 release. Check out the v3.x branch for v3.

Table of Contents

Quick start

Create a folder and make it your current working directory:

mkdir my-app
cd my-app

Generate a fastify project with npm init:

npm init fastify

Install dependencies:

npm i

To start the app in dev mode:

npm run dev

For production mode:

npm start

Under the hood npm init downloads and runs Fastify Create, which in turn uses the generate functionality of Fastify CLI.


To install Fastify in an existing project as a dependency:

Install with npm:

npm i fastify

Install with yarn:

yarn add fastify


// Require the framework and instantiate it

// ESM
import Fastify from 'fastify'
const fastify = Fastify({
  logger: true
// CommonJs
const fastify = require('fastify')({
  logger: true

// Declare a route
fastify.get('/', (request, reply) => {
  reply.send({ hello: 'world' })

// Run the server!
fastify.listen({ port: 3000 }, (err, address) => {
  if (err) throw err
  // Server is now listening on ${address}

with async-await:

// ESM
import Fastify from 'fastify'
const fastify = Fastify({
  logger: true
// CommonJs
const fastify = require('fastify')({
  logger: true

fastify.get('/', async (request, reply) => {
  return { hello: 'world' }

fastify.listen({ port: 3000 }, (err, address) => {
  if (err) throw err
  // Server is now listening on ${address}

Do you want to know more? Head to the Getting Started.

Fastify v1.x and v2.x

Code for Fastify's v1.x is in branch 1.x, so all Fastify 1.x related changes should be based on branch 1.x. In a similar way, all Fastify v2.x related changes should be based on branch 2.x.


.listen binds to the local host, localhost, interface by default ( or ::1, depending on the operating system configuration). If you are running Fastify in a container (Docker, GCP, etc.), you may need to bind to Be careful when deciding to listen on all interfaces; it comes with inherent security risks. See the documentation for more information.

Core features

  • Highly performant: as far as we know, Fastify is one of the fastest web frameworks in town, depending on the code complexity we can serve up to 76+ thousand requests per second.
  • Extensible: Fastify is fully extensible via its hooks, plugins and decorators.
  • Schema based: even if it is not mandatory we recommend to use JSON Schema to validate your routes and serialize your outputs, internally Fastify compiles the schema in a highly performant function.
  • Logging: logs are extremely important but are costly; we chose the best logger to almost remove this cost, Pino!
  • Developer friendly: the framework is built to be very expressive and help the developer in their daily use, without sacrificing performance and security.


Machine: EX41S-SSD, Intel Core i7, 4Ghz, 64GB RAM, 4C/8T, SSD.

Method:: autocannon -c 100 -d 40 -p 10 localhost:3000 * 2, taking the second average

Framework Version Router? Requests/sec
Express 4.17.3 14,200
hapi 20.2.1 42,284
Restify 8.6.1 50,363
Koa 2.13.0 54,272
Fastify 4.0.0 77,193
http.Server 16.14.2 74,513

Benchmarks taken using This is a synthetic, "hello world" benchmark that aims to evaluate the framework overhead. The overhead that each framework has on your application depends on your application, you should always benchmark if performance matters to you.




  • Core - Core plugins maintained by the Fastify team.
  • Community - Community supported plugins.
  • Live Examples - Multirepo with a broad set of real working examples.
  • Discord - Join our discord server and chat with the maintainers.


Please visit Fastify help to view prior support issues and to ask new support questions.


Fastify is the result of the work of a great community. Team members are listed in alphabetical order.

Lead Maintainers:

Fastify Core team

Fastify Plugins team

Great Contributors

Great contributors on a specific area in the Fastify ecosystem will be invited to join this group by Lead Maintainers.

Past Collaborators

Hosted by

We are a Growth Project in the OpenJS Foundation.


This project is kindly sponsored by:

Past Sponsors:

This list includes all companies that support one or more of the team members in the maintainance of this project.


Licensed under MIT.

For your convenience, here is a list of all the licenses of our production dependencies:

  • MIT
  • ISC
  • BSD-3-Clause
  • BSD-2-Clause