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3.3.9 • Public • Published

koa-better-body npm version License Libera Manifesto

Full-featured koa body parser! Support parsing text, buffer, json, json patch, json api, csp-report, multipart, form and urlencoded bodies. Works for koa@1, koa@2 and will work for koa@3.

Please consider following this project's author, Charlike Mike Reagent, and ⭐️ the project to show your ❤️ and support.

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If you have any how-to kind of questions, please read the Contributing Guide and Code of Conduct documents. For bugs reports and feature requests, please create an issue or ping @tunnckoCore at Twitter.

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Project is semantically versioned & automatically released from GitHub Actions with Lerna.

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Table of Contents

(TOC generated by verb using markdown-toc)


This project requires Node.js >=8.11 (see Support & Release Policy). Install it using yarn or npm.
We highly recommend to use Yarn when you think to contribute to this project.

$ yarn add koa-better-body


Generated using jest-runner-docs.


Robust body parser for koa@1, also works for koa@2 (with deprecations). Will also work for future koa@3 with koa-convert.




  • options {object} - see more on options section
  • returns {GeneratorFunction} - plugin for Koa


var koa = require('koa');
var body = require('koa-better-body');
var app = koa();
  .use(function* () {
    console.log(this.request.body); // if buffer or text
    console.log(this.request.files); // if multipart or urlencoded
    console.log(this.request.fields); // if json
  .listen(8080, function () {
    console.log('koa server start listening on port 8080');

Working with koa-router

using koa-router

'use strict';
var app = require('koa')();
var body = require('koa-better-body');
var router = require('koa-router')();
router.post('/upload', body(), function* (next) {
  // there's no `.body` when `multipart`,
  // `urlencoded` or `json` request
  // print it to the API requester
  this.body = JSON.stringify(
      fields: this.request.fields,
      files: this.request.files,
      body: this.request.body || null,
  yield next;
var format = require('util').format;
var host = 'http://localhost:4292';
var cmd = 'curl -i %s/upload -F "source=@%s/.editorconfig"';
console.log('Try it out with below CURL for `koa-better-body` repository.');
console.log(format(cmd, host, __dirname));


Sane defaults. ✨

Accepts JSON, JSON API v1, text, buffer, csp-report, multipart and urlencoded/form bodies. If you want to disallow accepting and parsing multipart body you should pass multipart: false. Most of the defaults you can see at utils.defaultOptions and utils.defaultTypes. All options are also been passed to formidable.IncomingForm! Even you can pass IncomingForm instance to be able to handle the different formidable events.

  • fields {Boolean|String}: Default false, which means it will set fields on this.request.fields. If you pass a string, for example 'foo', you will have fields on this.request.foo.
  • files {Boolean|String}: Default false, which means it will set files on this.request.files. If you pass a string, for example 'bar', you will have files on this.request.bar.
  • multipart {Boolean}: Default true. If you pass false it won't accept/parse multipart bodies.
  • textLimit {String}: Default '100kb'. Passed to bytes.parse method.
  • formLimit {String}: Default '100kb'. Passed to bytes.parse method.
  • urlencodedLimit {String}: Default '100kb'. Alias of opts.formLimit.
  • jsonLimit {String}: Default '100kb'. Passed to bytes.parse method.
  • bufferLimit {String}: Default '1mb'. Passed to bytes.parse method.
  • jsonStrict {Boolean}: Default true. When set to true, JSON parser will only accept arrays and objects.
  • detectJSON {Function}: Custom JSON request detect function - detectJSON(ctx).
  • strict {Boolean}: Default true. Pass false if you want to allow parsing GET, DELETE and HEAD requests.
  • onerror {Function}: Custom error handle, if throw an error, you can customize the response - onerror(err, ctx).
  • extendTypes {Object}: Default accepting types can find on utils.defaultTypes function. Allowing you to extend what your app can accept. By default works for JSON, JSON API v1, multipart, text, urlencoded and csp-report.
  • IncomingForm {IncomingForm}: Pass an instance of formidable.IncomingForm to be able to handle formidable events.
  • handler {GeneratorFunction}: Works with options.extendTypes.custom to handle custom types of content-type - handler(ctx, options, next). More info below.
  • querystring {Object}: Querystring module to be used. By default builtin querystring. More info below.
  • qs {Object}: Alias of opts.querystring. All opts are also passed to qs or querystring module.
  • delimiter {String}: Default is &. Delimiter of key/value pairs, passed to querystring lib
  • sep {String}: alias of opts.delimiter
  • buffer {Boolean}: Default false, pass true if you want to get body as buffer.

Note about options.extendTypes

ExandTypes option gives you a flexible way to handle different content-types and modify the defaults which can be found at utils.defaultTypes function. In addition you can pass combination of options.extendTypes.custom and options.handler. When the request has some of the "custom" content type, this middleware will call the handler generator function with ctx, options, next. You can see more at issue #52.

For example manually handle such content types foo/bar-x, text/quix:

const app = require('koa')()
const body = require('koa-better-body')
  textLimit: '300kb'
  extendTypes: {
    custom: [
  handler: function * (ctx, opts) {
    // `ctx` is equal to `this` and `app`
    // `opts` is current options object
    // passed to `koa-better-body`
    ctx.body = yield this.request.text(opts.textLimit)
app.use(function * showBody () {
  // `this.body` is text

Note about advanced querystring parsing

Because this middleware is fully based and integrated with koa-body-parsers, by default it uses Node's built-in module for that thing querystring. So if you have some issues with forms, think to add custom querystring module like qs to options.querystring or app.querystring. Related to this is issue #45.


const app = require('koa')()
const body = require('koa-better-body')
  multipart: false
  querystring: require('qs')

It's intentional that it's not included in the deps by default. In v2 it was also working by passing it to app.querystring, because koa-body-parsers works that way (index.js#L53).

Note about strict mode

We are trying to follow standards. 🐈

You can pass strict:false, but see IETF HTTP/1.1 Message Semantics: Section 6.1 to understand why we stay to "strict mode" by default. GET, HEAD, and DELETE requests have no defined semantics for the request body, but this doesn't mean they may not be valid in certain use cases. Last two tests at test/options.js are showing usage on non-strict and strict mode.

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See Also

Some of these projects are used here or were inspiration for this one, others are just related. So, thanks for your existance!

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Guides and Community

Please read the Contributing Guide and Code of Conduct documents for advices.

For bug reports and feature requests, please join our community forum and open a thread there with prefixing the title of the thread with the name of the project if there's no separate channel for it.

Consider reading the Support and Release Policy guide if you are interested in what are the supported Node.js versions and how we proceed. In short, we support latest two even-numbered Node.js release lines.

Support the project

Become a Partner or Sponsor? 💵 Check the OpenSource Commision (tier). 🎉 You can get your company logo, link & name on this file. It's also rendered on package's page in npmjs.com and yarnpkg.com sites too! 🚀

Not financial support? Okey! Pull requests, stars and all kind of contributions are always welcome. ✨


This project follows the all-contributors specification. Contributions of any kind are welcome!

Thanks goes to these wonderful people (emoji key), consider showing your support to them:

Charlike Mike Reagent

🚇 💻 📖 🤔 🚧 ⚠️

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Copyright (c) 2014-present, Charlike Mike Reagent <opensource@tunnckocore.com> & contributors.
Released under the MPL-2.0 License.


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