1xx InformationalExperimentalRFC 8297

103Early Hints

Preload resources while the server prepares the final response.

What it means

Allows the server to send preliminary response headers before the final response is ready. The browser can start preloading resources (CSS, JS, fonts) while the server is still generating the main response — improving page load performance.

When to use it

  • ✓Preloading critical CSS and JavaScript files
  • ✓Preconnecting to third-party origins
  • ✓Improving Time to First Byte (TTFB) performance

Code Examples

Early Hints with Next.js / Vercel
javascript
// Next.js supports Early Hints automatically
// Manual example in Node.js:
res.writeEarlyHints({
  link: '</styles.css>; rel=preload; as=style',
});
// Then send the actual response
res.status(200).send(html);

Don't confuse with

200

OK

Request succeeded.

Quick Facts

Code103
CategoryInformational
SpecRFC 8297
CommonNo

Relevant Headers

Link

Specifies resources to preload (e.g. <style.css>; rel=preload; as=style)

Related Codes

200OK
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