HTTP status codes are issued by a server in response to a client request. They are grouped into five classes: 1xx (Informational), 2xx (Success), 3xx (Redirection), 4xx (Client Error), and 5xx (Server Error). This reference covers all standard codes.
HTTP status codes are three-digit responses that web servers send to indicate the result of a client's request. They're grouped into five classes: 1xx (informational), 2xx (success), 3xx (redirection), 4xx (client error), and 5xx (server error). As a developer, you'll encounter these daily — a 200 means success, 301 is permanent redirect, 404 is not found, 403 is forbidden, 500 is internal server error. Understanding status codes is essential for debugging API integrations, configuring redirects, monitoring server health, and building proper error handling. This reference includes all standard codes plus common non-standard ones used by popular services.
200 OK — the request succeeded. You see it on every successful page load, API call, and resource fetch. It's so common that many tools only show non-200 codes to highlight issues.
301 is permanent redirect (browsers cache it, search engines transfer SEO value). 302 is temporary redirect (not cached, SEO stays with original URL). Use 301 for domain moves, 302 for temporary maintenance.
Server-side code crashed — unhandled exceptions, database connection failures, misconfigured servers, or resource exhaustion. Check server logs for the actual error. It's rarely the client's fault.
The server understood your request but refuses to authorize it. Common causes: wrong file permissions, IP restrictions, missing authentication, or WAF (Web Application Firewall) blocking. Different from 401 (not authenticated).
An April Fools' joke from 1998 (RFC 2324) that became a real HTTP status code. Some servers return it as an Easter egg. Google's teapot page at google.com/teapot is a famous example.