Key Features
Complete reference: all IANA-registered codes from 1xx through 5xx, plus nginx and Cloudflare codes (499, 520–530)
Plain-English explanations of when and why each code is sent — not just the spec name
Actionable fix lists for every common error: 400, 401, 403, 404, 429, 500, 502, 503, 504 and more
Instant search by code number or keyword ("timeout", "cloudflare", "redirect")
Filter by class — informational, success, redirect, client error, server error, non-standard
Spec references for every code (RFC 9110, RFC 6585, RFC 4918, and friends)
How to Use
1Type a status code (like 429) or a keyword (like "timeout") into the search box
2Optionally filter by class — 2xx, 4xx, 5xx, or non-standard
3Click any code to expand its full explanation, fix list, and spec reference
Common Use Cases
Debug a production error without tabbing to a search engine — search 502, read the fix list
Decide the right status code for the API you are building (201 vs 202, 401 vs 403, 422 vs 400)
Understand Cloudflare 52x codes that do not exist in any RFC
Learn HTTP properly — expandable cards double as a study reference with real-world context
Frequently Asked Questions
What is the difference between 401 and 403?
401 Unauthorized means the server does not know who you are — your credentials are missing or invalid. 403 Forbidden means it knows who you are and you are still not allowed. Retrying with the same credentials fixes 401, never 403.
What do Cloudflare 52x codes like 522 and 524 mean?
They are Cloudflare-specific: 521 means the origin refused the connection, 522 means the TCP handshake timed out, 524 means the connection worked but the origin took longer than ~100 seconds to respond. The fix is almost always on the origin server.
Which status code should my API return for validation errors?
Use 422 Unprocessable Content when the request is well-formed but fails business rules, and 400 Bad Request when the syntax itself is broken (invalid JSON, missing required fields). Rails, Laravel, and most modern APIs follow this convention.
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