409 Conflict

What This Error Means

The request conflicts with the current state of the server.

Request cannot be completed due to conflict with resource state.

Common Causes

• Version conflict
• Duplicate resource creation
• Concurrent modifications
• State mismatch

How to Fix It (For Visitors)

• Refresh the page and try again
• Resolve conflicts

How to Fix It (For Developers/Admins)

• Implement optimistic locking
• Use ETags for version control
• Handle concurrent updates
• Return conflict details in response

Code Examples

Here's how to return a 409 status code in various programming languages:

Python (Flask)

from flask import Flask, jsonify

app = Flask(__name__)

@app.route('/endpoint')
def endpoint():
    return jsonify({"message": "Conflict"}), 409

Node.js (Express)

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

app.get('/endpoint', (req, res) => {
    res.status(409).json({ message: 'Conflict' });
});

PHP

<?php
http_response_code(409);
header('Content-Type: application/json');
echo json_encode(['message' => 'Conflict']);
?>

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(409)
    json.NewEncoder(w).Encode(map[string]string{
        "message": "Conflict",
    })
}

Java (Spring Boot)

@GetMapping("/endpoint")
public ResponseEntity<Map<String, String>> endpoint() {
    Map<String, String> response = new HashMap<>();
    response.put("message", "Conflict");
    return ResponseEntity.status(409).body(response);
}

Ruby (Sinatra)

get '/endpoint' do
    status 409
    json message: 'Conflict'
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 6.5.8.

View on IANA HTTP Status Code Registry →