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  4. 103 Early Hints

103 Early Hints

Allow a client to request static assets while waiting for the HTML response.

To ensure Early Hints are enabled:

  1. Log in to the Cloudflare Dashboard and select your account and website.
  2. Go to Speed -> Optimization > Content Optimization.
  3. Enable the Early Hints toggle to on.

const CSS = "body { color: red; }";

const HTML = `
<!doctype html>
<html lang="en">
<head>
    <meta charset="utf-8">
    <title>Early Hints test</title>
    <link rel="stylesheet" href="/test.css">
</head>
<body>
    <h1>Early Hints test page</h1>
</body>
</html>
`;



export default {
  async fetch(req) {
    // If request is for test.css, serve the raw CSS
    if (/test\.css$/.test(req.url)) {
      return new Response(CSS, {
        headers: {
          "content-type": "text/css",
        },
      });
    } else {
      // Serve raw HTML using Early Hints for the CSS file
      return new Response(HTML, {
        headers: {
          "content-type": "text/html",
          link: "</test.css>; rel=preload; as=style",
        },
      });
    }
  },

};


const CSS = "body { color: red; }";

const HTML = `
<!doctype html>
<html lang="en">
<head>
    <meta charset="utf-8">
    <title>Early Hints test</title>
    <link rel="stylesheet" href="/test.css">
</head>
<body>
    <h1>Early Hints test page</h1>
</body>
</html>
`;



const handler: ExportedHandler = {
  async fetch(req) {
    // If request is for test.css, serve the raw CSS
    if (/test\.css$/.test(req.url)) {
      return new Response(CSS, {
        headers: {
          "content-type": "text/css",
        },
      });
    } else {
      // Serve raw HTML using Early Hints for the CSS file
      return new Response(HTML, {
        headers: {
          "content-type": "text/html",
          link: "</test.css>; rel=preload; as=style",
        },
      });
    }
  },

};



export default handler;