HTTP Error Reference

HTTP status codes are the foundational response language of the web. Every API call, page load, and resource fetch returns a three-digit code that tells the client what happened — whether the request succeeded, was redirected, failed due to a client error, or triggered a server-side fault. The current specification is RFC 9110 (June 2022), which consolidated and replaced earlier RFCs 7230–7235.

The five status code classes — 1xx informational, 2xx success, 3xx redirection, 4xx client error, and 5xx server error — map to distinct stages of request processing. Understanding which class a code belongs to is the first step in diagnosing whether the problem originates on the client side, the server side, or somewhere in between (such as a proxy or CDN).

FixerCode documents 58 HTTP status codes across 1 model, from well-known codes like 404 and 500 to less common responses like 103 Early Hints and 421 Misdirected Request. Each entry explains the protocol meaning, lists common causes, and links to related codes in the same response family.