https://unpkg.com/[email protected]/umd/react.production.js net::ERR_ABORTED 404 code example

Example: react cdn

<script crossorigin src="https://unpkg.com/react@16/umd/react.development.js"></script>
<script crossorigin src="https://unpkg.com/react-dom@16/umd/react-dom.development.js"></script>