CORS Error: Access Blocked

When a web page on https://app.example calls https://api.example, the browser enforces CORS. If the API omits Access-Control-Allow-Origin or blocks the preflight OPTIONS request, DevTools shows a network error that sounds like a failure to fetch even though the server returned 200.

Fixes belong on the API: return explicit allowed origins, forward methods and headers your client sends, and use Vary: Origin when appropriate. The SPA cannot "disable CORS"—only the server or a deliberate proxy can.

Read Nginx CORS or Express CORS after CORSFixer identifies your failure mode.