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 v5 release, which is not released/LTS yet.
Check out the 4.x branch for v4.

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.

Install

To install Fastify in an existing project as a dependency:

Install with npm:

npm i fastify

Install with yarn:

yarn add fastify

Example

// 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) => {
  reply.type('application/json').code(200)
  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.

Note

.listen binds to the local host, localhost, interface by default
(127.0.0.1 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 0.0.0.0. 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.

Benchmarks

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 https://github.com/fastify/benchmarks. 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.