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6.0.1 • Public • Published


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A full-featured koa body parser middleware. Supports multipart, urlencoded, and json request bodies. Provides the same functionality as Express's bodyParser - multer.


Install with npm

npm install koa-body


  • can handle requests such as:
    • multipart/form-data
    • application/x-www-form-urlencoded
    • application/json
    • application/json-patch+json
    • application/vnd.api+json
    • application/csp-report
    • text/xml
  • option for patch to Koa or Node, or either
  • file uploads
  • body, fields and files size limiting

Hello World - Quickstart

npm install koa koa-body # Note that Koa requires Node.js 7.6.0+ for async/await support


const Koa = require('koa');
const { koaBody } = require('koa-body');

const app = new Koa();

app.use((ctx) => {
  ctx.body = `Request Body: ${JSON.stringify(ctx.request.body)}`;

node index.js
curl -i http://localhost:3000/users -d "name=test"


HTTP/1.1 200 OK
Content-Type: text/plain; charset=utf-8
Content-Length: 29
Date: Wed, 03 May 2017 02:09:44 GMT
Connection: keep-alive

Request Body: {"name":"test"}%

For a more comprehensive example, see examples/multipart.js

Usage with koa-router

It's generally better to only parse the body as needed, if using a router that supports middleware composition, we can inject it only for certain routes.

const Koa = require('koa');
const app = new Koa();
const router = require('koa-router')();
const { koaBody } = require('koa-body');

router.post('/users', koaBody(), (ctx) => {
  // => POST body
  ctx.body = JSON.stringify(ctx.request.body);


console.log('curl -i http://localhost:3000/users -d "name=test"');

Usage with unsupported text body type

For unsupported text body type, for example, text/xml, you can use the unparsed request body at ctx.request.body. For the text content type, the includeUnparsed setting is not required.

// xml-parse.js:
const Koa = require('koa');
const { koaBody } = require('koa-body');
const convert = require('xml-js');

const app = new Koa();

app.use((ctx) => {
  const obj = convert.xml2js(ctx.request.body);
  ctx.body = `Request Body: ${JSON.stringify(obj)}`;

node xml-parse.js
curl -i http://localhost:3000/users -H "Content-Type: text/xml" -d '<?xml version="1.0"?><catalog id="1"></catalog>'


HTTP/1.1 200 OK
Content-Type: text/plain; charset=utf-8
Content-Length: 135
Date: Tue, 09 Jun 2020 11:17:38 GMT
Connection: keep-alive

Request Body: {"declaration":{"attributes":{"version":"1.0"}},"elements":[{"type":"element","name":"catalog","attributes":{"id":"1"}}]}%


Options available for koa-body. Four custom options, and others are from raw-body and formidable.

  • patchNode {Boolean} Patch request body to Node's ctx.req, default false
  • patchKoa {Boolean} Patch request body to Koa's ctx.request, default true
  • jsonLimit {String|Integer} The byte (if integer) limit of the JSON body, default 1mb
  • formLimit {String|Integer} The byte (if integer) limit of the form body, default 56kb
  • textLimit {String|Integer} The byte (if integer) limit of the text body, default 56kb
  • encoding {String} Sets encoding for incoming form fields, default utf-8
  • multipart {Boolean} Parse multipart bodies, default false
  • urlencoded {Boolean} Parse urlencoded bodies, default true
  • text {Boolean} Parse text bodies, such as XML, default true
  • json {Boolean} Parse JSON bodies, default true
  • jsonStrict {Boolean} Toggles co-body strict mode; if set to true - only parses arrays or objects, default true
  • includeUnparsed {Boolean} Toggles co-body returnRawBody option; if set to true, for form encoded and JSON requests the raw, unparsed request body will be attached to ctx.request.body using a Symbol (see details), default false
  • formidable {Object} Options to pass to the formidable multipart parser
  • onError {Function} Custom error handle, if throw an error, you can customize the response - onError(error, context), default will throw
  • parsedMethods {String[]} Declares the HTTP methods where bodies will be parsed, default ['POST', 'PUT', 'PATCH']. Replaces strict option.

A note about parsedMethods

see http://tools.ietf.org/html/draft-ietf-httpbis-p2-semantics-19#section-6.3

  • 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.
  • koa-body is strict by default, parsing only POST, PUT, and PATCH requests
  • you may use either the enumeration or strings to chose which methods to parse: For example, HttpMethodEnum.PATCH

File Support

Uploaded files are accessible via ctx.request.files.

A note about unparsed request bodies

Some applications require crytopgraphic verification of request bodies, for example webhooks from slack or stripe. The unparsed body can be accessed if includeUnparsed is true in koa-body's options. When enabled, import the symbol for accessing the request body from unparsed = require('koa-body/unparsed.js'), or define your own accessor using unparsed = Symbol.for('unparsedBody'). Then the unparsed body is available using ctx.request.body[unparsed].

Some options for formidable

See node-formidable for a full list of options

  • maxFields {Integer} Limits the number of fields that the querystring parser will decode, default 1000
  • maxFieldsSize {Integer} Limits the amount of memory all fields together (except files) can allocate in bytes. If this value is exceeded, an 'error' event is emitted, default 2mb (2 * 1024 * 1024)
  • uploadDir {String} Sets the directory for placing file uploads in, default os.tmpDir()
  • keepExtensions {Boolean} Files written to uploadDir will include the extensions of the original files, default false
  • hashAlgorithm {String} If you want checksums calculated for incoming files, set this to either 'sha1' or 'md5', default false
  • multiples {Boolean} Multiple file uploads or no, default true
  • onFileBegin {Function} Special callback on file begin. The function is executed directly by formidable. It can be used to rename files before saving them to disk. See the docs


Please see the Changelog for a summary of changes.


$ npm test


The MIT License, 2014 Charlike Mike Reagent (@tunnckoCore) and Daryl Lau (@daryllau)

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