Access-Control-Allow-Origin: * In Create React App, add "proxy": "http://localhost:5000" to package.json . Vue/Vite users can configure proxies in vite.config.js .
Access-Control-Allow-Origin: http://localhost:3000 Or for development:
(not recommended for regular browsing)
(development only) Extensions like Moesif CORS or Allow CORS can add the required headers on the fly — but never rely on this in production.