1xx

103 Early Hints

The server sends preliminary headers to let the browser preload resources.

What is HTTP 103?

This status code allows the server to send response headers before the final response is ready, primarily to let the browser start preloading resources like stylesheets, scripts, or fonts. It is used with Link headers to hint at resources the page will need, improving page load performance. The browser can begin fetching these resources while the server is still preparing the full response.

Defined in RFC 8297

Common Causes

  • Server is configured to send preload hints for critical CSS, JavaScript, or font files
  • Reverse proxies or CDNs sending early resource hints while the origin server processes the request
  • Performance optimization setups that separate header delivery from body generation

How to Fix

  • No fix needed; this improves performance by enabling resource preloading
  • To implement, configure your server or CDN to send Link headers with rel=preload before the final response
  • Ensure the hinted resources match what the final page actually needs to avoid wasted downloads