I've spent many hours solving this…

Cross-Origin Resource Sharing (CORS) errors are a regular part of web development. More info: MDN CORS Guide.

Issue 1: No Access-Control-Allow-Origin Header

Access to XMLHttpRequest blocked by CORS policy:
No 'Access-Control-Allow-Origin' header is present on the requested resource.

The frontend is calling a backend endpoint without proper CORS configuration. Fix:

'allowed_origins' => [
    'http://localhost:3000',
    'http://localhost:5173',
],

For Laravel 11+:

php artisan config:publish cors

Then edit config/cors.php. Most frameworks have built-in CORS support — look for config files or middleware.

Issue 2: Credentials with Wildcard Origins

The 'Access-Control-Allow-Origin' header value must not be '*' when the
request's credentials mode is 'include'.

Using withCredentials: true with allowed_origins: ['*'] is not allowed by browsers. Specify exact trusted origins:

const api = axios.create({
  baseURL: "http://127.0.0.1:8000",
  withCredentials: true,
});

'allowed_origins' => ['https://yourdomain.com'], // NOT ['*']
'supports_credentials' => true,

Issue 3: Wrong API Endpoint

Calling /login instead of /api/login — accidentally hitting the web route instead of the API route.

# Check your routes first
php artisan route:list | grep login

// Fix the endpoint
const response = await api.post('/api/login', data); // Add /api prefix

Issue 4: Config Changes Not Applied

# Clear all cache in Laravel
php artisan optimize:clear

# Restart dev server
ctrl + c
npm run dev

Most problems stem from configuration mismatches rather than complex setup issues.

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