Is fastify free and open source?

Yes. fastify is open source, available under the MIT license.

Is fastify actively maintained?

fastify is actively maintained — the latest commit landed within the last month. Its health score is 100/100.

How popular is fastify?

fastify has 36.5k GitHub stars and about 8.4M downloads per week.

Does fastify have known security vulnerabilities?

10 known security advisories are listed for fastify in the OSV database.

What are some alternatives to fastify?

Alternatives to fastify include Express, Koa, Hapi, NestJS and Restify.

fastify

JavaScript MIT★ 36,487

100

Health 100/100

Baseline50
Commit recency+25
Popularity+20
Adoption+15
Security-20
Release cadence+10
Open-issue load+5

Fastify is a high-performance Node.js web framework built around a powerful plugin/encapsulation architecture and JSON Schema-based validation and serialization. It aims to minimize per-request overhead while keeping a clean, developer-friendly API for building HTTP APIs and services.

http-server json-schema nodejs performance pino-logging plugins typescript web-framework

Raw .md

Embed badge

[![health](https://opensources.dev/resource/fastify/badge.svg)](https://opensources.dev/resource/fastify)

MITPermissive — free to use in commercial and proprietary software, with attribution.View license →

Production readiness

4/5

Actively maintainedCommits in the last 6 months
No known vulnerabilities10 known OSV advisories
Clear, usable licenseMIT (permissive)
Proven adoptionWidely used
Has documentationDocumentation indexed

Install

npm install fastify

Downloads8.4M /wk

MomentumRising ↑ 81%

Security10 known advisoriesGHSA-247c-9743-5963 GHSA-3fjj-p79j-c9hh GHSA-444r-cwp2-x5xf

Bundle size129.8 KB gzipped15 dependencies

MaintenanceActively maintainedIs fastify still maintained? →

Our analysis

Fastify is a Node.js web framework focused on low overhead and high throughput, combining a schema-driven approach to request validation/response serialization with an encapsulated plugin system.

When to use fastify

Choose Fastify when building HTTP APIs or microservices in Node.js where request throughput, low latency, and structured validation matter. Its JSON Schema integration is ideal for well-defined contracts, and its plugin/encapsulation model scales cleanly across large modular codebases. Strong TypeScript support and built-in Pino logging make it a solid default for new production services.

When not to

If you have an existing Express codebase with heavy reliance on Express-specific middleware, migrating may not be worth it. For very small scripts or one-off endpoints, a minimal framework or raw http may suffice. Teams wanting a fully opinionated, batteries-included architecture with DI and decorators may prefer NestJS; those targeting edge/runtime-agnostic deployment may prefer Hono.

Strengths

Excellent benchmark performance with low framework overhead
JSON Schema validation and fast compiled serialization built in
Mature plugin architecture with encapsulation for clean modularity
First-class TypeScript types and integrated structured logging via Pino
Large ecosystem of official and community plugins

Trade-offs

Schema-first patterns and plugin encapsulation have a learning curve compared to Express
Express middleware is not directly compatible (requires adapters)
Plugin loading order and decorators can confuse newcomers
Older major versions reach EOL and require paid support for continued security fixes

Maturity

Very mature and production-proven, with ~36k stars, an active core/plugins team led by experienced maintainers (Matteo Collina et al.), defined LTS policy, and a broad plugin ecosystem. Currently on v5.

Documentation from fastify, shown under MIT with attribution. Source: https://www.fastify.dev

An efficient server implies a lower cost of the infrastructure, 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 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. Check out the 4.x branch for v4.

Quick start
Install
Example
Core features
Benchmarks
Documentation
Ecosystem
Support
Team
Hosted by
License

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:

npm i 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. If you learn best by reading code, explore the official demo.

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 listening 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 using 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 developers 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

FrameworkVersionRouter?Requests/secExpress4.17.3✓14,200hapi20.2.1✓42,284Restify8.6.1✓50,363Koa2.13.0✗54,272Fastify4.0.0✓77,193-http.Server16.14.2✗74,513

These 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.

Documentation

Ecosystem

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.

Support

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

Version 3 of Fastify and lower are EOL and will not receive any security or bug fixes.

Fastify's partner, HeroDevs, provides commercial security fixes for all unsupported versions at https://herodevs.com/support/fastify-nes. Fastify's supported version matrix is available in the Long Term Support documentation.

Contributing

Whether reporting bugs, discussing improvements and new ideas, or writing code, we welcome contributions from anyone and everyone. Please read the CONTRIBUTING guidelines before submitting pull requests.

Team

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

Emeritus Contributors

Great contributors to a specific area of the Fastify ecosystem will be invited to join this group by Lead Maintainers when they decide to step down from the active contributor's group.

Hosted by

We are an At-Large Project in the OpenJS Foundation.

Acknowledgments

This project is kindly sponsored by:

Past Sponsors:

LetzDoIt

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

License

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

View on GitHub

On this page

Table of Contents
Quick start
Install
Example
Core features
Benchmarks
Documentation
Ecosystem
Support
Contributing
Team
Fastify Core team
Fastify Plugins team
Emeritus Contributors
Hosted by
Sponsors
Acknowledgments
License

fastify

JavaScript MIT★ 36,487

100

Health 100/100

Baseline50
Commit recency+25
Popularity+20
Adoption+15
Security-20
Release cadence+10
Open-issue load+5

http-server json-schema nodejs performance pino-logging plugins typescript web-framework

Raw .md

Embed badge

[![health](https://opensources.dev/resource/fastify/badge.svg)](https://opensources.dev/resource/fastify)

MITPermissive — free to use in commercial and proprietary software, with attribution.View license →

Production readiness

4/5

Actively maintainedCommits in the last 6 months
No known vulnerabilities10 known OSV advisories
Clear, usable licenseMIT (permissive)
Proven adoptionWidely used
Has documentationDocumentation indexed

Install

npm install fastify

Downloads8.4M /wk

MomentumRising ↑ 81%

Security10 known advisoriesGHSA-247c-9743-5963 GHSA-3fjj-p79j-c9hh GHSA-444r-cwp2-x5xf

Bundle size129.8 KB gzipped15 dependencies

MaintenanceActively maintainedIs fastify still maintained? →

Our analysis

Fastify is a Node.js web framework focused on low overhead and high throughput, combining a schema-driven approach to request validation/response serialization with an encapsulated plugin system.

When to use fastify

When not to

Strengths

Excellent benchmark performance with low framework overhead
JSON Schema validation and fast compiled serialization built in
Mature plugin architecture with encapsulation for clean modularity
First-class TypeScript types and integrated structured logging via Pino
Large ecosystem of official and community plugins

Trade-offs

Schema-first patterns and plugin encapsulation have a learning curve compared to Express
Express middleware is not directly compatible (requires adapters)
Plugin loading order and decorators can confuse newcomers
Older major versions reach EOL and require paid support for continued security fixes

Maturity

Documentation from fastify, shown under MIT with attribution. Source: https://www.fastify.dev

The main branch refers to the Fastify v5 release. Check out the 4.x branch for v4.

Quick start
Install
Example
Core features
Benchmarks
Documentation
Ecosystem
Support
Team
Hosted by
License

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:

npm i 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. If you learn best by reading code, explore the official demo.

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 listening 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 using 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 developers 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

FrameworkVersionRouter?Requests/secExpress4.17.3✓14,200hapi20.2.1✓42,284Restify8.6.1✓50,363Koa2.13.0✗54,272Fastify4.0.0✓77,193-http.Server16.14.2✗74,513

Documentation

Ecosystem

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.

Support

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

Version 3 of Fastify and lower are EOL and will not receive any security or bug fixes.

Contributing

Team

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

Emeritus Contributors

Great contributors to a specific area of the Fastify ecosystem will be invited to join this group by Lead Maintainers when they decide to step down from the active contributor's group.

Hosted by

We are an At-Large Project in the OpenJS Foundation.

Acknowledgments

This project is kindly sponsored by:

Past Sponsors:

LetzDoIt

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

License

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

View on GitHub

On this page

Table of Contents
Quick start
Install
Example
Core features
Benchmarks
Documentation
Ecosystem
Support
Contributing
Team
Fastify Core team
Fastify Plugins team
Emeritus Contributors
Hosted by
Sponsors
Acknowledgments
License

Production readiness

Our analysis

When to use fastify

When not to

Strengths

Trade-offs

Maturity

Table of Contents

Quick start

Install

Example

Note

Core features

Benchmarks

Documentation

Ecosystem

Support

Contributing

Team

Fastify Core team

Fastify Plugins team

Emeritus Contributors

Hosted by

Sponsors

Acknowledgments

License

Alternatives see all →

More in Frameworks

vue

andrej-karpathy-skills

next.js

react-native

immich

fastapi

Frequently asked questions

Production readiness

Our analysis

When to use fastify

When not to

Strengths

Trade-offs

Maturity

Table of Contents

Quick start

Install

Example

Note

Core features

Benchmarks

Documentation

Ecosystem

Support

Contributing

Team

Fastify Core team

Fastify Plugins team

Emeritus Contributors

Hosted by

Sponsors

Acknowledgments

License

Alternatives see all →

More in Frameworks

vue

andrej-karpathy-skills

next.js

react-native

immich

fastapi

Frequently asked questions