100 Continue

What This Error Means

The server has received the request headers and the client should proceed to send the request body.

The initial part of a request has been received and the client should continue with the request.

Common Causes

• Request has Expect: 100-continue header
• Server agrees to receive request body

How to Fix It (For Visitors)

• This is not an error - continue sending the request

How to Fix It (For Developers/Admins)

• Handle 100 Continue responses in HTTP client
• Continue sending request body after receiving this status

Code Examples

Here's how to return a 100 status code in various programming languages:

Python (Flask)

from flask import Flask, jsonify

app = Flask(__name__)

@app.route('/endpoint')
def endpoint():
    return jsonify({"message": "Continue"}), 100

Node.js (Express)

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

app.get('/endpoint', (req, res) => {
    res.status(100).json({ message: 'Continue' });
});

PHP

<?php
http_response_code(100);
header('Content-Type: application/json');
echo json_encode(['message' => 'Continue']);
?>

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(100)
    json.NewEncoder(w).Encode(map[string]string{
        "message": "Continue",
    })
}

Java (Spring Boot)

@GetMapping("/endpoint")
public ResponseEntity<Map<String, String>> endpoint() {
    Map<String, String> response = new HashMap<>();
    response.put("message", "Continue");
    return ResponseEntity.status(100).body(response);
}

Ruby (Sinatra)

get '/endpoint' do
    status 100
    json message: 'Continue'
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 7231 Section 6.2.1.

View on IANA HTTP Status Code Registry →