HTTP Status Codes Reference

Quick reference for HTTP status codes grouped by class, with live search and a one-line description for every code.

About HTTP Status Codes

HTTP status codes are three-digit numbers that a server returns with every response, grouped by their first digit: 1xx is informational (the request is being processed, e.g. 100 Continue), 2xx means success (200 OK, 201 Created), 3xx means the client must take additional action, usually a redirect (301 Moved Permanently, 304 Not Modified), 4xx means the request was invalid from the client's side (400 Bad Request, 404 Not Found), and 5xx means the server failed while handling an otherwise valid request (500 Internal Server Error, 503 Service Unavailable). Knowing the class at a glance tells you which side of the connection to investigate first.

This reference is most useful when debugging APIs and troubleshooting failures: curl or your browser's network panel shows the code, and the description here tells you what it means and where to look next. A few common traps are worth remembering: 200 means the request was fulfilled, while 201 specifically means a resource was created — many APIs return 200 for POSTs that should be 201; 429 Too Many Requests means you are rate-limited and should respect the Retry-After header instead of hammering the endpoint; 418 I'm a Teapot is an April Fools' joke that real servers sometimes return deliberately; and 404 can mean "not found" or, when a server wants to hide the existence of a resource, a masked 403.