404 Not Found

What This Error Means

The server cannot find the requested resource.

The URL you're trying to access doesn't exist on the server.

Common Causes

• URL typo or incorrect link
• Resource deleted or moved
• Route not defined
• File doesn't exist

How to Fix It (For Visitors)

• Check URL for typos
• Use site search to find content
• Return to homepage
• Clear browser cache

How to Fix It (For Developers/Admins)

• Verify file exists on server
• Check route configuration
• Review URL rewrite rules
• Implement custom 404 page
• Check for broken links

Code Examples

Here's how to return a 404 status code in various programming languages:

Python (Flask)

from flask import Flask, jsonify

app = Flask(__name__)

@app.route('/endpoint')
def endpoint():
    return jsonify({"message": "Not Found"}), 404

Node.js (Express)

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

app.get('/endpoint', (req, res) => {
    res.status(404).json({ message: 'Not Found' });
});

PHP

<?php
http_response_code(404);
header('Content-Type: application/json');
echo json_encode(['message' => 'Not Found']);
?>

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(404)
    json.NewEncoder(w).Encode(map[string]string{
        "message": "Not Found",
    })
}

Java (Spring Boot)

@GetMapping("/endpoint")
public ResponseEntity<Map<String, String>> endpoint() {
    Map<String, String> response = new HashMap<>();
    response.put("message", "Not Found");
    return ResponseEntity.status(404).body(response);
}

Ruby (Sinatra)

get '/endpoint' do
    status 404
    json message: 'Not Found'
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 6.5.4.

View on IANA HTTP Status Code Registry →