How to Fix CORS Error in Angular: Simple Steps

A CORS error in Angular happens because the browser blocks requests to a different domain without proper permission. To fix it, configure your backend server to allow cross-origin requests or use Angular's proxy configuration to route API calls through the same origin.

Why This Happens

CORS (Cross-Origin Resource Sharing) errors occur when your Angular app tries to call an API on a different domain or port, and the server does not explicitly allow your app's origin. Browsers block these requests to protect users from malicious sites.

javascript

fetch('http://api.example.com/data')
  .then(response => response.json())
  .then(data => console.log(data));

Output

Access to fetch at 'http://api.example.com/data' from origin 'http://localhost:4200' has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource.

The Fix

Fix the CORS error by enabling CORS on your backend server to allow requests from your Angular app's origin. Alternatively, use Angular's proxy configuration to forward API calls through the Angular development server, avoiding cross-origin requests.

json

{
  "/api": {
    "target": "http://api.example.com",
    "secure": false,
    "changeOrigin": true,
    "logLevel": "debug"
  }
}

// In angular.json, add:
// "serve": {
//   "options": {
//     "proxyConfig": "src/proxy.conf.json"
//   }
// }

Output

API calls to /api/* are forwarded to http://api.example.com without CORS errors.

Prevention

Always configure your backend to allow CORS for trusted origins. Use Angular proxy during development to avoid CORS issues. Test API calls early to catch CORS problems. Keep backend and frontend origins consistent in production.

Related Errors

Other common errors include 401 Unauthorized when authentication fails, and 404 Not Found when API endpoints are incorrect. Fix these by checking API URLs and authentication tokens.

Key Takeaways

CORS errors happen because browsers block cross-origin requests without permission.

Enable CORS on your backend or use Angular proxy to fix these errors.

Use Angular proxy config during development to avoid CORS issues easily.

Always test API calls early to catch and fix CORS problems.

Keep backend CORS settings secure by allowing only trusted origins.