Skip to content


Switch branches/tags

Name already in use

A tag already exists with the provided branch name. Many Git commands accept both tag and branch names, so creating this branch may cause unexpected behavior. Are you sure you want to create this branch?


CI NPM version NPM downloads JavaScript Style Guide

A simple plugin for Fastify that adds a content type parser for the content type application/x-www-form-urlencoded.

This branch targets Fastify v4. Please refer to this branch and related versions for Fastify ^2.0.0 compatibility.

For Fastify v3 support, please use @fastify/formbody ^6.0.1.


Given the following code:

const fastify = require('fastify')()

fastify.register(require('@fastify/formbody'))'/', (req, reply) => {

fastify.listen({ port: 8000 }, (err) => {
  if (err) throw err

And a POST body of:


The sent reply would be the object:

  foo: 'foo',
  bar: 'bar',
  answer: 42


The plugin accepts an options object with the following properties:

  • bodyLimit: The maximum amount of bytes to process before returning an error. If the limit is exceeded, a 500 error will be returned immediately. When set to undefined the limit will be set to whatever is configured on the parent Fastify instance. The default value is whatever is configured in fastify (1048576 by default).
  • parser: The default parser used is the querystring.parse built-in. You can change this default by passing a parser function e.g. fastify.register(require('@fastify/formbody'), { parser: str => myParser(str) })

Upgrading from 4.x

Previously, the external qs lib was used that did things like parse nested objects. For example:

  • Input: foo[one]=foo&foo[two]=bar
  • Parsed: { foo: { one: 'foo', two: 'bar' } }

The way this is handled now using the built-in querystring.parse:

  • Input: foo[one]=foo&foo[two]=bar
  • Parsed: { 'foo[one]': 'foo', 'foo[two]': 'bar' }

If you need nested parsing, you must configure it manually by installing the qs lib (npm i qs), and then configure an optional parser:

const fastify = require('fastify')()
const qs = require('qs')
fastify.register(require('@fastify/formbody'), { parser: str => qs.parse(str) })


Licensed under MIT