103 Early Hints

103

Early Hints

Example HTTP Response

HTTP Response

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

Common Causes

Preloading resources while server prepares response
Sending Link headers early for faster page loads
Optimizing perceived performance

Technical Details

What does this mean?

A sneak peek! The server is giving you hints about what's coming, like a movie trailer before the main feature.

Technical Definition

Used to return some response headers before final HTTP message.

RFC Says

"The 103 (Early Hints) informational status code indicates to the client that the server is likely to send a final response with the header fields included in the informational response."

Plain English:

The server is giving you a preview of what resources you'll need (like CSS and JavaScript files) before the final response is ready. This lets your browser start downloading them immediately for better performance.

View RFC Documentation

Code Snippets

Ready-to-use code for returning this HTTP status in your application:

Node.js

// Express.js
app.get('/example', (req, res) => {
  res.status(103).json({
    error: 'Early Hints',
    message: 'Your error message here'
  });
});

// Native HTTP
const http = require('http');

http.createServer((req, res) => {
  res.writeHead(103, { 'Content-Type': 'application/json' });
  res.end(JSON.stringify({
    error: 'Early Hints',
    message: 'Your error message here'
  }));
}).listen(3000);

From the Blog

Understanding HTTP 103 Early Hints: Faster Pages with Smarter Preloads
How HTTP 103 Early Hints lets the server tell the browser what to preload before the real response is ready — what it does, when it helps, and how to ship it.
8 min read

103 Early Hints FAQ

What causes a 103 Early Hints error?

Preloading resources while server prepares response. Sending Link headers early for faster page loads. Optimizing perceived performance.