HTTP Status Codes: What Browsers Are Really Telling You

HTTP status codes are the server's way of giving you quick feedback. They are grouped into five logical categories.

1xx: Informational

Rarely seen. These mean "I've received your request, keep going."

2xx: Success

200 OK is the gold standard. 201 Created is used after a successful POST request.

3xx: Redirection

301 Moved Permanently is critical for SEO. 304 Not Modified tells the browser to use its local cache.

4xx: Client Errors

You did something wrong. 403 Forbidden means you don't have permission. 404 Not Found means the URL is wrong.

5xx: Server Errors

The code or the machine failed. 500 Internal Server Error is the generic "crash" code. 503 Service Unavailable usually means the server is overloaded.