Do you need a CORS proxy in React Native or Expo?

Usually not — and if you add one where you don't need it, you're adding latency and a dependency for nothing. But some parts of a React Native app really do run inside a browser engine, and there CORS is exactly as real as it is on the web. Here's how to tell which one you're dealing with.

Aug 22, 2026 · ~5 min read

The short version

CORS is a restriction the browser enforces on JavaScript it's running, checking response headers before handing the response back to your code. React Native's JS engine (Hermes or JSC) is not a browser — fetch() called from a native screen talks straight to the network with no CORS layer in the way at all. If your native fetch() call is failing, it is almost never a CORS error, no matter what the symptom looks like.

Where it doesn't apply

• Standard React Native screens — fetch() or axios called from your normal app code, running on-device via Hermes/JSC. No CORS.
• Expo Go on a physical device or simulator — same JS engine, same answer. No CORS.

If a request fails here, look at: the actual HTTP status code, network permissions (Android's cleartext-traffic block on plain http://, iOS App Transport Security), or a genuine server-side error. A CORS-shaped fix won't touch any of these.

Where it does apply

• Expo Web / React Native Web — expo start --web or any RN Web build runs your app as actual JavaScript inside an actual browser. Full CORS enforcement, identical to any other web app.
• WebView-based screens — react-native-webview, or a Capacitor/Cordova-style hybrid wrapper, renders a real browser engine (WKWebView / Chromium) inside your native app. JS running inside that WebView is browser JS. CORS applies.

The fix in both cases is identical to any web app:

// Fails with a CORS error — only in the web / WebView target
fetch('https://api.example.com/data')

// Works
const target = encodeURIComponent('https://api.example.com/data');
fetch(`https://api.corsproxy.dev/proxy?url=${target}&key=YOUR_CORSPROXY_KEY`)
  .then(r => r.json())
  .then(data => console.log(data));

The practical pattern for a codebase that targets both

If you ship the same code to native and web (Expo's whole pitch), branch on platform rather than routing every request through a proxy unconditionally — native doesn't need it and the extra hop is pure latency there:

import { Platform } from 'react-native';

async function fetchData(url) {
  const needsProxy = Platform.OS === 'web';
  const finalUrl = needsProxy
    ? `https://api.corsproxy.dev/proxy?url=${encodeURIComponent(url)}&key=YOUR_CORSPROXY_KEY`
    : url;
  const res = await fetch(finalUrl);
  return res.json();
}