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Version: 0.83

Networking

Many mobile apps need to load resources from a remote URL. You may want to make a POST request to a REST API, or you may need to fetch a chunk of static content from another server.

Using Fetch​

React Native provides the Fetch API for your networking needs. Fetch will seem familiar if you have used XMLHttpRequest or other networking APIs before. You may refer to MDN's guide on Using Fetch for additional information.

Making requests​

In order to fetch content from an arbitrary URL, you can pass the URL to fetch:

TypeScript
fetch('https://mywebsite.com/mydata.json');

Fetch also takes an optional second argument that allows you to customize the HTTP request. You may want to specify additional headers, or make a POST request:

TypeScript
fetch('https://mywebsite.com/endpoint/', {
  method: 'POST',
  headers: {
    Accept: 'application/json',
    'Content-Type': 'application/json',
  },
  body: JSON.stringify({
    firstParam: 'yourValue',
    secondParam: 'yourOtherValue',
  }),
});

Take a look at the Fetch Request docs for a full list of properties.

Handling the response​

The above examples show how you can make a request. In many cases, you will want to do something with the response.

Networking is an inherently asynchronous operation. Fetch method will return a Promise that makes it straightforward to write code that works in an asynchronous manner:

TypeScript
const getMoviesFromApi = () => {
  return fetch('https://reactnative.dev/movies.json')
    .then(response => response.json())
    .then(json => {
      return json.movies;
    })
    .catch(error => {
      console.error(error);
    });
};

You can also use the async / await syntax in a React Native app:

TypeScript
const getMoviesFromApiAsync = async () => {
  try {
    const response = await fetch(
      'https://reactnative.dev/movies.json',
    );
    const json = await response.json();
    return json.movies;
  } catch (error) {
    console.error(error);
  }
};

Don't forget to catch any errors that may be thrown by fetch, otherwise they will be dropped silently.

info

By default, iOS enforces App Transport Security (ATS), requiring any HTTP connection to use HTTPS. If you need to fetch from a cleartext URL (one that begins with http), you must configure an ATS exception in your Info.plist file using NSAppTransportSecurity. It is recommended to add exceptions only for specific domains using NSExceptionDomains rather than disabling ATS globally (NSAllowsArbitraryLoads), as Apple's App Store review requires justification for disabling ATS. See Apple's documentation on Preventing Insecure Network Connections for more information.

tip

On Android, as of API Level 28, clear text traffic is also blocked by default. This behaviour can be overridden by setting android:usesCleartextTraffic in the app manifest file.

Using Other Networking Libraries​

The XMLHttpRequest API is built into React Native. This means that you can use third party libraries such as frisbee or axios that depend on it, or you can use the XMLHttpRequest API directly if you prefer.

TypeScript
const request = new XMLHttpRequest();
request.onreadystatechange = e => {
  if (request.readyState !== 4) {
    return;
  }

  if (request.status === 200) {
    console.log('success', request.responseText);
  } else {
    console.warn('error');
  }
};

request.open('GET', 'https://mywebsite.com/endpoint/');
request.send();
Caution

The security model for XMLHttpRequest is different than on web as there is no concept of CORS in native apps.

WebSocket Support​

React Native also supports WebSockets, a protocol which provides full-duplex communication channels over a single TCP connection.

TypeScript
const ws = new WebSocket('ws://host.com/path');

ws.onopen = () => {
  // connection opened
  ws.send('something'); // send a message