# Send a JSON response using Express

> Learn how to send a JSON response in Express using the Response.json() method, which takes an object or array and converts it to JSON before sending it.

Author: [Flavio Copes](https://flaviocopes.com/about/) | Published: 2018-09-01 | Topics: [Express.js](https://flaviocopes.com/tags/express/) | Canonical: https://flaviocopes.com/express-send-json-response/

When you listen for connections on a route in Express, the callback function will be invoked on every network call with a Request object instance and a Response object instance.

Example:

```js
app.get('/', (req, res) => res.send('Hello World!'))
```

Here we used the `Response.send()` method, which accepts any string.

You can send [JSON](https://flaviocopes.com/json/) to the client by using `Response.json()`, a useful method.

It accepts an object or array, and converts it to JSON before sending it (if you want to inspect or validate the JSON your API returns, try my [JSON formatter](https://flaviocopes.com/tools/json-formatter/)):

```js
res.json({ username: 'Flavio' })
```