? 404 Not Found

? Quick Overview

The 404 Not Found status code is an HTTP response sent by a server when the requested resource cannot be found. It means the server is reachable, but the specific URL or file does not exist.

? Key Concepts

Client-side error (4xx category)
Resource does not exist on the server
URL may be incorrect, deleted, or moved
Server is working correctly

? Syntax / Theory

When a browser requests a URL, the server searches for the requested resource. If it cannot locate the file or route, it responds with status code 404.

Status Line: HTTP/1.1 404 Not Found
No authentication issue
No server crash

? Code Example(s)

? View Code Example

// Example of sending a 404 response using Node.js
res.status(404).send("Page not found");

? View Code Example

// PHP example for returning a 404 status code
http_response_code(404);
echo "404 - Page Not Found";

? Live Output / Explanation

What Happens?

The browser displays a 404 error page. This may be a default server page or a custom-designed error page created by the developer.

? Interactive Example

Use the simulator below to send requests to a fake server and see the status code response:

Waiting for request...

? View Static Code Logic

// Visiting a missing route like this will trigger a 404
https://example.com/this-page-does-not-exist

? Use Cases

Handling broken or outdated links
Displaying custom error pages
Improving SEO by properly signaling missing pages
User-friendly navigation fallback

✅ Tips & Best Practices

Create custom 404 pages with helpful navigation
Log 404 errors to identify broken links
Avoid redirecting all 404s to the homepage
Return correct HTTP status codes

? Try It Yourself

Create a custom 404 HTML page
Configure 404 handling in Apache or Nginx
Return 404 from a backend API
Test missing routes in your application