HTTP Status Codes

Initial part of a request received; client should continue with remainder of request.

Server agrees to switch protocols (e.g. HTTP to WebSocket via Upgrade header).

The request has been fulfilled, resulting in the creation of a new resource.

The server successfully fulfilled the request and there is no additional content to send in the payload.

Target resource has been assigned a new permanent URI. Search engines transfer link equity.

Indicates the client has the latest version cached (matching ETag or If-Modified-Since).

Directs client to resource with same HTTP method guaranteed (e.g. POST remains POST).

Server cannot process request due to client error (e.g. malformed JSON body or invalid syntax).

Request requires user authentication. WWW-Authenticate header should be provided.

Server understands the request but refuses to authorize it (insufficient permissions / RBAC).

The origin server did not find a current representation for the target resource.

User has sent too many requests in a given amount of time ("rate limiting").

The server encountered an unexpected condition that prevented it from fulfilling the request.

The server, while acting as a gateway or proxy, received an invalid response from upstream.

The server is currently unable to handle the request due to temporary overloading or maintenance.