HTTP status code

The HTTP 103 status code stands for "Early Hints". It is an informational response used to help the client start processing resources earlier while the server is still preparing the final response.

When is HTTP 103 Used?

• It is primarily used with HTTP/2 and HTTP/3 to improve page load performance.
• The server sends an early response with preload hints (e.g., Link headers for CSS, JS, images) so the browser can start fetching resources before receiving the final response.

Example Scenario

When a browser requests a webpage, the server may take some time to generate the HTML. Instead of making the browser wait, the server sends a 103 Early Hints response with preload instructions for assets like stylesheets and scripts.

Example

Server Sends Early Hints:

    
        HTTP/1.1 103 Early Hints
        Link: </style.css>; rel=preload; as=style
        Link: </script.js>; rel=preload; as=script
    

Final Response (Once Ready)

    
        HTTP/1.1 200 OK
        Content-Type: text/html
    

Summary

HTTP 103 is an optimization feature that allows clients to start loading resources before the final response arrives, improving webpage performance.