103 Early Hints

What This Error Means

Used to return some response headers before final HTTP message.

Allows the server to send preliminary response headers while it prepares the full response.

Common Causes

• Server sending Link headers for preloading resources
• Performance optimization

How to Fix It (For Visitors)

• This is not an error - performance optimization in progress

How to Fix It (For Developers/Admins)

• Use to preload critical resources
• Send Link headers for CSS, JS, fonts

Code Examples

Here's how to return a 103 status code in various programming languages:

Python (Flask)

from flask import Flask, jsonify

app = Flask(__name__)

@app.route('/endpoint')
def endpoint():
    return jsonify({"message": "Early Hints"}), 103

Node.js (Express)

const express = require('express');
const app = express();

app.get('/endpoint', (req, res) => {
    res.status(103).json({ message: 'Early Hints' });
});

PHP

<?php
http_response_code(103);
header('Content-Type: application/json');
echo json_encode(['message' => 'Early Hints']);
?>

Go

package main

import (
    "encoding/json"
    "net/http"
)

func handler(w http.ResponseWriter, r *http.Request) {
    w.Header().Set("Content-Type", "application/json")
    w.WriteHeader(103)
    json.NewEncoder(w).Encode(map[string]string{
        "message": "Early Hints",
    })
}

Java (Spring Boot)

@GetMapping("/endpoint")
public ResponseEntity<Map<String, String>> endpoint() {
    Map<String, String> response = new HashMap<>();
    response.put("message", "Early Hints");
    return ResponseEntity.status(103).body(response);
}

Ruby (Sinatra)

get '/endpoint' do
    status 103
    json message: 'Early Hints'
end

Browser Compatibility

Browser	Support	Notes
Chrome	✓ Full Support	All versions
Firefox	✓ Full Support	All versions
Safari	✓ Full Support	All versions
Edge	✓ Full Support	All versions

Official Specification

This status code is defined in RFC 8297.

View on IANA HTTP Status Code Registry →