RFC 9110, IANA registry
HTTP Status Codes Reference
Three digit codes, grouped 1xx to 5xx, that describe the result of an HTTP request and tell you which side of the connection failed.
At a glance
Key factsStandard
Classes
Five, from 1xx to 5xx
Success
2xx, request accepted
Rate limited
429, honor Retry-After
Where it comes from
HTTP status codes are defined by RFC 9110 and registered with the Internet Assigned Numbers Authority, so their meanings are stable across every server and client. The first digit sets the class: 1xx informational, 2xx success, 3xx redirection, 4xx client error, and 5xx server error. That single digit answers the first question in any debugging session.
How to use it
Read the class before the specific code. A 4xx means the request itself was wrong, so look at what you sent. A 5xx means the server failed a request that may have been valid, so the problem is on its side. Learn the everyday codes: 200 and 201 for success, 301 and 304 for redirects and caching, 400 through 404 for client errors, 429 for rate limiting, and 500 through 504 for server and gateway failures.
This page is a standing summary. For the interactive tool and the full tables, open the http status codes page. The data here is compiled from HTTP semantics, defined by RFC 9110 and the IANA status code registry.