Single-purpose koa middleware to parse valid JSON request bodies and nothing else.

Usage no npm install needed!

<script type="module">
  import koaJsonBody from 'https://cdn.skypack.dev/koa-json-body';



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A single-purpose koa middleware to only parse JSON request bodies and nothing else.

By default, this libarary parses all valid JSON bodies on POST, PUT, and PATCH requests, and assigns the value to ctx.request.body.

If there is a JSON parsing error, or if the request is not of valid type, ctx.request.body is not set, and will be undefined. If the JSON request payload is too large (by default, the limit is 1mb), a 413 Payload Too Large error will be thrown.

To ensure ctx.request.body contains an empty object {} (rather than undefined) on missing/invalid payloads, you can set the fallback option to true.


yarn add koa-json-body

or via npm:

npm install koa-json-body --save


  • fallback - when set to true, ctx.request.body will always contain {} upon missing or invalid payloads. (default: false)
  • limit - number or string representing the request size limit (default: 1mb)
  • strict - when set to true, koa-json-body will only accept arrays and objects. (default: true)

Additional options available via co-body.


On a every route:

const body = require('koa-json-body')

app.use(body({ limit: '10kb', fallback: true }))

app.use((ctx, next) => {

On a per-route basis (this example uses koa-router):

const body = require('koa-json-body')({ limit: '10kb' })

app.post('/users', body, (ctx, next) => {


To test, simply run

yarn test

Made for koa 2 and beyond

For koa 0.x and 1.x support, see the koa-1 branch.