rsnext/docs/api-routes/api-middlewares.md

---
description: API Routes provide built-in middlewares that parse the incoming request. Learn more about them here.
---

# API Middlewares

API routes provide built in middlewares which parse the incoming request (`req`). Those middlewares are:

- `req.cookies` - An object containing the cookies sent by the request. Defaults to `{}`
- `req.query` - An object containing the [query string](https://en.wikipedia.org/wiki/Query_string). Defaults to `{}`
- `req.body` - An object containing the body parsed by `content-type`, or `null` if no body was sent

## Custom config

Every API route can export a `config` object to change the default configs, which are the following:

```js
export const config = {
  api: {
    bodyParser: {
      sizeLimit: '1mb',
    },
  },
}
```

The `api` object includes all configs available for API routes.

`bodyParser` Enables body parsing, you can disable it if you want to consume it as a `Stream`:

```js
export const config = {
  api: {
    bodyParser: false,
  },
}
```

`bodyParser.sizeLimit` is the maximum size allowed for the parsed body, in any format supported by [bytes](https://github.com/visionmedia/bytes.js), like so:

```js
export const config = {
  api: {
    bodyParser: {
      sizeLimit: '500kb',
    },
  },
}
```

## Connect/Express middleware support

You can also use [Connect](https://github.com/senchalabs/connect) compatible middleware.

For example, [configuring CORS](https://developer.mozilla.org/en-US/docs/Web/HTTP/CORS) for your API endpoint can be done leveraging the [cors](https://www.npmjs.com/package/cors) package.

First, install `cors`:

```bash
npm i cors
# or
yarn add cors
```

Now, let's add `cors` to the API route:

```js
import Cors from 'cors'

// Initializing the cors middleware
const cors = Cors({
  methods: ['GET', 'HEAD'],
})

// Helper method to wait for a middleware to execute before continuing
// And to throw an error when an error happens in a middleware
function runMiddleware(req, res, fn) {
  return new Promise((resolve, reject) => {
    fn(req, res, result => {
      if (result instanceof Error) {
        return reject(result)
      }

      return resolve(result)
    })
  })
}

async function handler(req, res) {
  // Run the middleware
  await runMiddleware(req, res, cors)

  // Rest of the API logic
  res.json({ message: 'Hello Everyone!' })
}

export default handler
```