{ "100": { "code": 100, "phrase": "Continue", "category": "Informational", "source": "IANA", "rfc": "RFC9110", "specUrl": "https://datatracker.ietf.org/doc/html/rfc9110#section-15.2.1", "description": "The initial part of a request has been received and the client should continue to send the remainder of the request, or ignore the response if the request is already complete.", "expectsEmptyBody": true, "cacheability": "uncacheable", "requiresAuth": false, "safeForMethods": "all", "relatedHeaders": [ { "name": "Expect", "required": false, "purpose": "Originating request header that triggers a 100 response." } ], "aliases": [], "deprecated": false, "guidance": { "isRetryable": false, "retryStrategy": "never", "agentAction": "Continue sending the request body; treat as a successful handshake.", "commonCauses": [ "Client sent Expect: 100-continue before a large body." ], "relatedStatuses": [ 417 ] } }, "101": { "code": 101, "phrase": "Switching Protocols", "category": "Informational", "source": "IANA", "rfc": "RFC9110", "specUrl": "https://datatracker.ietf.org/doc/html/rfc9110#section-15.2.2", "description": "The server understands and is willing to comply with the client request, via the Upgrade header field, for a change in the application protocol being used on this connection.", "expectsEmptyBody": true, "cacheability": "uncacheable", "requiresAuth": false, "safeForMethods": "all", "relatedHeaders": [ { "name": "Upgrade", "required": true, "purpose": "Lists the protocol(s) being switched to." }, { "name": "Connection", "required": true, "purpose": "Must include \"Upgrade\"." } ], "aliases": [], "deprecated": false, "guidance": { "isRetryable": false, "retryStrategy": "never", "agentAction": "Switch to the protocol named in the Upgrade header (e.g., WebSocket).", "commonCauses": [ "Client requested protocol upgrade (WebSocket, HTTP/2 cleartext)." ], "relatedStatuses": [ 426 ] } }, "102": { "code": 102, "phrase": "Processing", "category": "Informational", "source": "IANA", "rfc": "RFC2518", "specUrl": "https://datatracker.ietf.org/doc/html/rfc2518#section-10.1", "description": "WebDAV interim response indicating that the server has accepted the complete request but has not yet completed it. Deprecated by some clients.", "expectsEmptyBody": true, "cacheability": "uncacheable", "requiresAuth": false, "safeForMethods": "all", "relatedHeaders": [], "aliases": [], "deprecated": true, "guidance": { "isRetryable": false, "retryStrategy": "never", "agentAction": "Keep the connection open and wait for the final response.", "commonCauses": [ "Long-running WebDAV operation." ], "relatedStatuses": [] } }, "103": { "code": 103, "phrase": "Early Hints", "category": "Informational", "source": "IANA", "rfc": "RFC8297", "specUrl": "https://datatracker.ietf.org/doc/html/rfc8297#section-2", "description": "Used to return some response headers before the final HTTP message, typically to allow the client to preload resources via Link headers.", "expectsEmptyBody": true, "cacheability": "uncacheable", "requiresAuth": false, "safeForMethods": "all", "relatedHeaders": [ { "name": "Link", "required": false, "purpose": "Preload/preconnect hints sent before the final response." } ], "aliases": [], "deprecated": false, "guidance": { "isRetryable": false, "retryStrategy": "never", "agentAction": "Begin preloading hinted resources while awaiting the final response.", "commonCauses": [ "Server-driven preload hints to reduce page load time." ], "relatedStatuses": [] } }, "200": { "code": 200, "phrase": "OK", "category": "Success", "source": "IANA", "rfc": "RFC9110", "specUrl": "https://datatracker.ietf.org/doc/html/rfc9110#section-15.3.1", "description": "The request has succeeded. The payload sent depends on the request method.", "expectsEmptyBody": false, "cacheability": "heuristic", "requiresAuth": false, "safeForMethods": "all", "relatedHeaders": [], "aliases": [], "deprecated": false, "guidance": { "isRetryable": false, "retryStrategy": "never", "agentAction": "Parse and use the response body.", "commonCauses": [ "Standard successful request." ], "relatedStatuses": [ 201, 204, 206 ] } }, "201": { "code": 201, "phrase": "Created", "category": "Success", "source": "IANA", "rfc": "RFC9110", "specUrl": "https://datatracker.ietf.org/doc/html/rfc9110#section-15.3.2", "description": "The request has been fulfilled and has resulted in one or more new resources being created. The primary resource URI is given by Location.", "expectsEmptyBody": false, "cacheability": "uncacheable", "requiresAuth": false, "safeForMethods": "all", "relatedHeaders": [ { "name": "Location", "required": false, "purpose": "URI of the newly created resource." } ], "aliases": [], "deprecated": false, "guidance": { "isRetryable": false, "retryStrategy": "never", "agentAction": "Read the Location header for the new resource URI.", "commonCauses": [ "Successful POST or PUT that created a resource." ], "relatedStatuses": [ 200, 202 ] } }, "202": { "code": 202, "phrase": "Accepted", "category": "Success", "source": "IANA", "rfc": "RFC9110", "specUrl": "https://datatracker.ietf.org/doc/html/rfc9110#section-15.3.3", "description": "The request has been accepted for processing, but the processing has not been completed. The request might or might not be eventually acted upon.", "expectsEmptyBody": false, "cacheability": "uncacheable", "requiresAuth": false, "safeForMethods": "all", "relatedHeaders": [], "aliases": [], "deprecated": false, "guidance": { "isRetryable": false, "retryStrategy": "never", "agentAction": "Poll the indicated status endpoint or wait for an async callback.", "commonCauses": [ "Async job submission, batch processing." ], "relatedStatuses": [ 201, 303 ] } }, "203": { "code": 203, "phrase": "Non-Authoritative Information", "category": "Success", "source": "IANA", "rfc": "RFC9110", "specUrl": "https://datatracker.ietf.org/doc/html/rfc9110#section-15.3.4", "description": "The request was successful but the enclosed payload has been modified by a transforming proxy from that of the origin server.", "expectsEmptyBody": false, "cacheability": "heuristic", "requiresAuth": false, "safeForMethods": "all", "relatedHeaders": [], "aliases": [], "deprecated": false, "guidance": { "isRetryable": false, "retryStrategy": "never", "agentAction": "Treat as 200 OK but be aware the body may have been transformed by an intermediary.", "commonCauses": [ "Transforming proxy modified the response." ], "relatedStatuses": [ 200 ] } }, "204": { "code": 204, "phrase": "No Content", "category": "Success", "source": "IANA", "rfc": "RFC9110", "specUrl": "https://datatracker.ietf.org/doc/html/rfc9110#section-15.3.5", "description": "The server has successfully fulfilled the request and there is no additional content to send in the response payload body.", "expectsEmptyBody": true, "cacheability": "heuristic", "requiresAuth": false, "safeForMethods": "all", "relatedHeaders": [], "aliases": [], "deprecated": false, "guidance": { "isRetryable": false, "retryStrategy": "never", "agentAction": "Do not attempt to parse a body; treat as success.", "commonCauses": [ "Successful DELETE or PUT/PATCH that returns no body." ], "relatedStatuses": [ 200, 205 ] } }, "205": { "code": 205, "phrase": "Reset Content", "category": "Success", "source": "IANA", "rfc": "RFC9110", "specUrl": "https://datatracker.ietf.org/doc/html/rfc9110#section-15.3.6", "description": "The server has fulfilled the request and desires that the user agent reset the document view which caused the request to be sent.", "expectsEmptyBody": true, "cacheability": "uncacheable", "requiresAuth": false, "safeForMethods": "all", "relatedHeaders": [], "aliases": [], "deprecated": false, "guidance": { "isRetryable": false, "retryStrategy": "never", "agentAction": "Clear the originating form or input view.", "commonCauses": [ "Form submission that should reset on success." ], "relatedStatuses": [ 204 ] } }, "206": { "code": 206, "phrase": "Partial Content", "category": "Success", "source": "IANA", "rfc": "RFC9110", "specUrl": "https://datatracker.ietf.org/doc/html/rfc9110#section-15.3.7", "description": "The server is successfully fulfilling a range request for the target resource by transferring one or more parts of the selected representation.", "expectsEmptyBody": false, "cacheability": "heuristic", "requiresAuth": false, "safeForMethods": [ "GET", "HEAD" ], "relatedHeaders": [ { "name": "Content-Range", "required": true, "purpose": "Indicates which byte range is in the body." }, { "name": "Accept-Ranges", "required": false, "purpose": "Indicates supported range units." } ], "aliases": [], "deprecated": false, "guidance": { "isRetryable": false, "retryStrategy": "never", "agentAction": "Assemble the byte range with previously fetched parts; resume support.", "commonCauses": [ "Range request for video, large file, or resumable download." ], "relatedStatuses": [ 200, 416 ] } }, "207": { "code": 207, "phrase": "Multi-Status", "category": "Success", "source": "IANA", "rfc": "RFC4918", "specUrl": "https://datatracker.ietf.org/doc/html/rfc4918#section-11.1", "description": "WebDAV: provides status for multiple independent operations in a single response (multistatus XML).", "expectsEmptyBody": false, "cacheability": "uncacheable", "requiresAuth": false, "safeForMethods": "all", "relatedHeaders": [], "aliases": [], "deprecated": false, "guidance": { "isRetryable": false, "retryStrategy": "never", "agentAction": "Parse the multistatus XML body for per-resource status codes.", "commonCauses": [ "WebDAV PROPFIND, PROPPATCH, COPY, MOVE, DELETE on collections." ], "relatedStatuses": [ 208 ] } }, "208": { "code": 208, "phrase": "Already Reported", "category": "Success", "source": "IANA", "rfc": "RFC5842", "specUrl": "https://datatracker.ietf.org/doc/html/rfc5842#section-7.1", "description": "WebDAV: used inside a 207 Multi-Status response to avoid repeatedly enumerating internal members of multiple bindings to the same collection.", "expectsEmptyBody": false, "cacheability": "uncacheable", "requiresAuth": false, "safeForMethods": "all", "relatedHeaders": [], "aliases": [], "deprecated": false, "guidance": { "isRetryable": false, "retryStrategy": "never", "agentAction": "Treat as already-enumerated; do not re-fetch.", "commonCauses": [ "WebDAV bindings already reported in the same multistatus." ], "relatedStatuses": [ 207 ] } }, "226": { "code": 226, "phrase": "IM Used", "category": "Success", "source": "IANA", "rfc": "RFC3229", "specUrl": "https://datatracker.ietf.org/doc/html/rfc3229#section-10.4.1", "description": "The server has fulfilled a GET request for the resource, and the response is a representation of the result of one or more instance-manipulations applied to the current instance.", "expectsEmptyBody": false, "cacheability": "heuristic", "requiresAuth": false, "safeForMethods": [ "GET" ], "relatedHeaders": [ { "name": "IM", "required": false, "purpose": "Instance manipulation applied." }, { "name": "Delta-Base", "required": false, "purpose": "Base entity tag for delta encoding." } ], "aliases": [], "deprecated": false, "guidance": { "isRetryable": false, "retryStrategy": "never", "agentAction": "Apply the delta to the cached representation.", "commonCauses": [ "Delta-encoded HTTP response." ], "relatedStatuses": [ 200 ] } }, "300": { "code": 300, "phrase": "Multiple Choices", "category": "Redirection", "source": "IANA", "rfc": "RFC9110", "specUrl": "https://datatracker.ietf.org/doc/html/rfc9110#section-15.4.1", "description": "The target resource has more than one representation, each with its own more specific identifier, and information about the alternatives is provided.", "expectsEmptyBody": false, "cacheability": "heuristic", "requiresAuth": false, "safeForMethods": "all", "relatedHeaders": [ { "name": "Location", "required": false, "purpose": "Server-preferred alternative URI." } ], "aliases": [], "deprecated": false, "guidance": { "isRetryable": false, "retryStrategy": "never", "agentAction": "Pick a representation from the listed alternatives or follow Location if provided.", "commonCauses": [ "Content negotiation with multiple acceptable variants." ], "relatedStatuses": [ 301, 302, 303 ] } }, "301": { "code": 301, "phrase": "Moved Permanently", "category": "Redirection", "source": "IANA", "rfc": "RFC9110", "specUrl": "https://datatracker.ietf.org/doc/html/rfc9110#section-15.4.2", "description": "The target resource has been assigned a new permanent URI and any future references to this resource ought to use the enclosed URI.", "expectsEmptyBody": false, "cacheability": "heuristic", "requiresAuth": false, "safeForMethods": "all", "relatedHeaders": [ { "name": "Location", "required": true, "purpose": "New permanent URI." } ], "aliases": [], "deprecated": false, "guidance": { "isRetryable": false, "retryStrategy": "never", "agentAction": "Follow Location; update bookmarks/links to the new URI.", "commonCauses": [ "Permanent URL change, domain migration, HTTPS upgrade." ], "relatedStatuses": [ 308, 302 ] } }, "302": { "code": 302, "phrase": "Found", "category": "Redirection", "source": "IANA", "rfc": "RFC9110", "specUrl": "https://datatracker.ietf.org/doc/html/rfc9110#section-15.4.3", "description": "The target resource resides temporarily under a different URI. The client should continue to use the original request URI for future requests.", "expectsEmptyBody": false, "cacheability": "uncacheable", "requiresAuth": false, "safeForMethods": "all", "relatedHeaders": [ { "name": "Location", "required": true, "purpose": "Temporary URI." } ], "aliases": [ "Moved Temporarily" ], "deprecated": false, "guidance": { "isRetryable": false, "retryStrategy": "never", "agentAction": "Follow Location for this request only; do not cache the redirect.", "commonCauses": [ "Temporary redirect, post-login redirect." ], "relatedStatuses": [ 303, 307 ] } }, "303": { "code": 303, "phrase": "See Other", "category": "Redirection", "source": "IANA", "rfc": "RFC9110", "specUrl": "https://datatracker.ietf.org/doc/html/rfc9110#section-15.4.4", "description": "The server is redirecting the user agent to a different resource, as indicated by Location, that is intended to provide an indirect response to the original request.", "expectsEmptyBody": false, "cacheability": "uncacheable", "requiresAuth": false, "safeForMethods": "all", "relatedHeaders": [ { "name": "Location", "required": true, "purpose": "Target URI to GET." } ], "aliases": [], "deprecated": false, "guidance": { "isRetryable": false, "retryStrategy": "never", "agentAction": "Issue a GET to Location regardless of the original method.", "commonCauses": [ "Post/Redirect/Get pattern after form submission." ], "relatedStatuses": [ 302, 307 ] } }, "304": { "code": 304, "phrase": "Not Modified", "category": "Redirection", "source": "IANA", "rfc": "RFC9110", "specUrl": "https://datatracker.ietf.org/doc/html/rfc9110#section-15.4.5", "description": "Indicates that the conditional request would have resulted in a 200 OK response if it were not for the fact that the condition evaluated to false.", "expectsEmptyBody": true, "cacheability": "uncacheable", "requiresAuth": false, "safeForMethods": [ "GET", "HEAD" ], "relatedHeaders": [ { "name": "ETag", "required": false, "purpose": "Validator matching the cached representation." }, { "name": "Cache-Control", "required": false, "purpose": "Freshness directives." }, { "name": "Vary", "required": false, "purpose": "Headers that affected selection." } ], "aliases": [], "deprecated": false, "guidance": { "isRetryable": false, "retryStrategy": "never", "agentAction": "Serve from the local cache; the cached representation is still fresh.", "commonCauses": [ "Conditional GET with If-None-Match or If-Modified-Since matched." ], "relatedStatuses": [ 200, 412 ] } }, "305": { "code": 305, "phrase": "Use Proxy", "category": "Redirection", "source": "IANA", "rfc": "RFC9110", "specUrl": "https://datatracker.ietf.org/doc/html/rfc9110#section-15.4.6", "description": "Deprecated. The requested resource must be accessed through a specified proxy.", "expectsEmptyBody": false, "cacheability": "uncacheable", "requiresAuth": false, "safeForMethods": "all", "relatedHeaders": [], "aliases": [], "deprecated": true, "guidance": { "isRetryable": false, "retryStrategy": "never", "agentAction": "Ignore; modern clients must not honor 305 for security reasons.", "commonCauses": [ "Legacy proxy configuration." ], "relatedStatuses": [] } }, "307": { "code": 307, "phrase": "Temporary Redirect", "category": "Redirection", "source": "IANA", "rfc": "RFC9110", "specUrl": "https://datatracker.ietf.org/doc/html/rfc9110#section-15.4.8", "description": "The target resource resides temporarily under a different URI and the user agent MUST NOT change the request method when following the redirect.", "expectsEmptyBody": false, "cacheability": "uncacheable", "requiresAuth": false, "safeForMethods": "all", "relatedHeaders": [ { "name": "Location", "required": true, "purpose": "Temporary URI." } ], "aliases": [], "deprecated": false, "guidance": { "isRetryable": false, "retryStrategy": "never", "agentAction": "Follow Location with the same method and body.", "commonCauses": [ "Temporary redirect where method preservation matters (e.g., POST)." ], "relatedStatuses": [ 302, 308 ] } }, "308": { "code": 308, "phrase": "Permanent Redirect", "category": "Redirection", "source": "IANA", "rfc": "RFC9110", "specUrl": "https://datatracker.ietf.org/doc/html/rfc9110#section-15.4.9", "description": "The target resource has been assigned a new permanent URI and the user agent MUST NOT change the request method when following the redirect.", "expectsEmptyBody": false, "cacheability": "heuristic", "requiresAuth": false, "safeForMethods": "all", "relatedHeaders": [ { "name": "Location", "required": true, "purpose": "New permanent URI." } ], "aliases": [], "deprecated": false, "guidance": { "isRetryable": false, "retryStrategy": "never", "agentAction": "Follow Location with the same method; update stored references.", "commonCauses": [ "Permanent move where method preservation matters." ], "relatedStatuses": [ 301, 307 ] } }, "400": { "code": 400, "phrase": "Bad Request", "category": "Client Error", "source": "IANA", "rfc": "RFC9110", "specUrl": "https://datatracker.ietf.org/doc/html/rfc9110#section-15.5.1", "description": "The server cannot or will not process the request due to something that is perceived to be a client error (e.g., malformed syntax, invalid framing).", "expectsEmptyBody": false, "cacheability": "uncacheable", "requiresAuth": false, "safeForMethods": "all", "relatedHeaders": [], "aliases": [], "deprecated": false, "guidance": { "isRetryable": false, "retryStrategy": "never", "agentAction": "Fix the request payload or syntax; do not retry as-is.", "commonCauses": [ "Malformed JSON", "Missing required field", "Invalid header syntax" ], "relatedStatuses": [ 422, 415 ] } }, "401": { "code": 401, "phrase": "Unauthorized", "category": "Client Error", "source": "IANA", "rfc": "RFC9110", "specUrl": "https://datatracker.ietf.org/doc/html/rfc9110#section-15.5.2", "description": "The request has not been applied because it lacks valid authentication credentials for the target resource.", "expectsEmptyBody": false, "cacheability": "uncacheable", "requiresAuth": true, "safeForMethods": "all", "relatedHeaders": [ { "name": "WWW-Authenticate", "required": true, "purpose": "Challenge describing the auth scheme." } ], "aliases": [], "deprecated": false, "guidance": { "isRetryable": false, "retryStrategy": "never", "agentAction": "Acquire valid credentials and retry with an Authorization header.", "commonCauses": [ "Missing or expired token", "Wrong credentials", "Token revoked" ], "relatedStatuses": [ 403, 407 ] } }, "402": { "code": 402, "phrase": "Payment Required", "category": "Client Error", "source": "IANA", "rfc": "RFC9110", "specUrl": "https://datatracker.ietf.org/doc/html/rfc9110#section-15.5.3", "description": "Reserved for future use. Originally intended for digital payment systems.", "expectsEmptyBody": false, "cacheability": "uncacheable", "requiresAuth": false, "safeForMethods": "all", "relatedHeaders": [], "aliases": [], "deprecated": false, "guidance": { "isRetryable": false, "retryStrategy": "never", "agentAction": "Surface payment/billing requirement to the user; do not auto-retry.", "commonCauses": [ "API quota exhausted on paid tier", "Subscription expired" ], "relatedStatuses": [ 403, 429 ] } }, "403": { "code": 403, "phrase": "Forbidden", "category": "Client Error", "source": "IANA", "rfc": "RFC9110", "specUrl": "https://datatracker.ietf.org/doc/html/rfc9110#section-15.5.4", "description": "The server understood the request but refuses to authorize it. Re-authenticating will not help.", "expectsEmptyBody": false, "cacheability": "uncacheable", "requiresAuth": false, "safeForMethods": "all", "relatedHeaders": [], "aliases": [], "deprecated": false, "guidance": { "isRetryable": false, "retryStrategy": "never", "agentAction": "Do not retry; the principal lacks permission for this resource.", "commonCauses": [ "Insufficient role/scope", "IP blocked", "CSRF check failed" ], "relatedStatuses": [ 401, 451 ] } }, "404": { "code": 404, "phrase": "Not Found", "category": "Client Error", "source": "IANA", "rfc": "RFC9110", "specUrl": "https://datatracker.ietf.org/doc/html/rfc9110#section-15.5.5", "description": "The origin server did not find a current representation for the target resource or is not willing to disclose that one exists.", "expectsEmptyBody": false, "cacheability": "heuristic", "requiresAuth": false, "safeForMethods": "all", "relatedHeaders": [], "aliases": [], "deprecated": false, "guidance": { "isRetryable": false, "retryStrategy": "never", "agentAction": "Verify the URL; do not retry unless the resource is expected to appear later.", "commonCauses": [ "Typo in URL", "Resource deleted", "Privacy-preserving hide of 403" ], "relatedStatuses": [ 410, 403 ] } }, "405": { "code": 405, "phrase": "Method Not Allowed", "category": "Client Error", "source": "IANA", "rfc": "RFC9110", "specUrl": "https://datatracker.ietf.org/doc/html/rfc9110#section-15.5.6", "description": "The method received in the request-line is known by the origin server but not supported by the target resource.", "expectsEmptyBody": false, "cacheability": "heuristic", "requiresAuth": false, "safeForMethods": "all", "relatedHeaders": [ { "name": "Allow", "required": true, "purpose": "Lists the methods supported by the target resource." } ], "aliases": [], "deprecated": false, "guidance": { "isRetryable": false, "retryStrategy": "never", "agentAction": "Inspect Allow header and reissue with a permitted method.", "commonCauses": [ "Wrong HTTP verb for the endpoint." ], "relatedStatuses": [ 501 ] } }, "406": { "code": 406, "phrase": "Not Acceptable", "category": "Client Error", "source": "IANA", "rfc": "RFC9110", "specUrl": "https://datatracker.ietf.org/doc/html/rfc9110#section-15.5.7", "description": "The target resource does not have a current representation that would be acceptable to the user agent according to the proactive negotiation header fields.", "expectsEmptyBody": false, "cacheability": "uncacheable", "requiresAuth": false, "safeForMethods": "all", "relatedHeaders": [ { "name": "Accept", "required": false, "purpose": "Originating preference header." } ], "aliases": [], "deprecated": false, "guidance": { "isRetryable": false, "retryStrategy": "never", "agentAction": "Relax Accept/Accept-Language constraints and retry.", "commonCauses": [ "No representation matches the client's Accept headers." ], "relatedStatuses": [ 415 ] } }, "407": { "code": 407, "phrase": "Proxy Authentication Required", "category": "Client Error", "source": "IANA", "rfc": "RFC9110", "specUrl": "https://datatracker.ietf.org/doc/html/rfc9110#section-15.5.8", "description": "Similar to 401 but indicates that the client needs to authenticate itself in order to use a proxy.", "expectsEmptyBody": false, "cacheability": "uncacheable", "requiresAuth": true, "safeForMethods": "all", "relatedHeaders": [ { "name": "Proxy-Authenticate", "required": true, "purpose": "Proxy auth challenge." } ], "aliases": [], "deprecated": false, "guidance": { "isRetryable": false, "retryStrategy": "never", "agentAction": "Supply Proxy-Authorization and retry.", "commonCauses": [ "Corporate proxy requiring authentication." ], "relatedStatuses": [ 401 ] } }, "408": { "code": 408, "phrase": "Request Timeout", "category": "Client Error", "source": "IANA", "rfc": "RFC9110", "specUrl": "https://datatracker.ietf.org/doc/html/rfc9110#section-15.5.9", "description": "The server did not receive a complete request message within the time that it was prepared to wait.", "expectsEmptyBody": false, "cacheability": "uncacheable", "requiresAuth": false, "safeForMethods": "all", "relatedHeaders": [], "aliases": [], "deprecated": false, "guidance": { "isRetryable": true, "retryStrategy": "exponential-backoff", "agentAction": "Retry the request with backoff; consider increasing client timeout.", "commonCauses": [ "Slow client", "Network congestion", "Idle keep-alive connection closed" ], "relatedStatuses": [ 504 ] } }, "409": { "code": 409, "phrase": "Conflict", "category": "Client Error", "source": "IANA", "rfc": "RFC9110", "specUrl": "https://datatracker.ietf.org/doc/html/rfc9110#section-15.5.10", "description": "The request could not be completed due to a conflict with the current state of the target resource.", "expectsEmptyBody": false, "cacheability": "uncacheable", "requiresAuth": false, "safeForMethods": "all", "relatedHeaders": [], "aliases": [], "deprecated": false, "guidance": { "isRetryable": false, "retryStrategy": "never", "agentAction": "Re-read the current resource state and resolve the conflict before resubmitting.", "commonCauses": [ "Concurrent edit collision", "Duplicate resource creation", "Version mismatch" ], "relatedStatuses": [ 412, 428 ] } }, "410": { "code": 410, "phrase": "Gone", "category": "Client Error", "source": "IANA", "rfc": "RFC9110", "specUrl": "https://datatracker.ietf.org/doc/html/rfc9110#section-15.5.11", "description": "Access to the target resource is no longer available at the origin server and this condition is likely to be permanent.", "expectsEmptyBody": false, "cacheability": "heuristic", "requiresAuth": false, "safeForMethods": "all", "relatedHeaders": [], "aliases": [], "deprecated": false, "guidance": { "isRetryable": false, "retryStrategy": "never", "agentAction": "Remove any cached references; do not retry.", "commonCauses": [ "Permanently deleted resource." ], "relatedStatuses": [ 404 ] } }, "411": { "code": 411, "phrase": "Length Required", "category": "Client Error", "source": "IANA", "rfc": "RFC9110", "specUrl": "https://datatracker.ietf.org/doc/html/rfc9110#section-15.5.12", "description": "The server refuses to accept the request without a defined Content-Length.", "expectsEmptyBody": false, "cacheability": "uncacheable", "requiresAuth": false, "safeForMethods": [ "POST", "PUT", "PATCH" ], "relatedHeaders": [ { "name": "Content-Length", "required": true, "purpose": "Length of the request body in octets." } ], "aliases": [], "deprecated": false, "guidance": { "isRetryable": false, "retryStrategy": "never", "agentAction": "Add Content-Length and retry.", "commonCauses": [ "Chunked transfer rejected by server." ], "relatedStatuses": [] } }, "412": { "code": 412, "phrase": "Precondition Failed", "category": "Client Error", "source": "IANA", "rfc": "RFC9110", "specUrl": "https://datatracker.ietf.org/doc/html/rfc9110#section-15.5.13", "description": "One or more conditions given in the request header fields evaluated to false when tested on the server.", "expectsEmptyBody": false, "cacheability": "uncacheable", "requiresAuth": false, "safeForMethods": "all", "relatedHeaders": [ { "name": "If-Match", "required": false, "purpose": "Originating precondition." }, { "name": "If-Unmodified-Since", "required": false, "purpose": "Originating precondition." } ], "aliases": [], "deprecated": false, "guidance": { "isRetryable": false, "retryStrategy": "never", "agentAction": "Re-fetch current ETag/Last-Modified and retry with the new validator.", "commonCauses": [ "Stale If-Match", "Optimistic concurrency control mismatch" ], "relatedStatuses": [ 409, 428 ] } }, "413": { "code": 413, "phrase": "Content Too Large", "category": "Client Error", "source": "IANA", "rfc": "RFC9110", "specUrl": "https://datatracker.ietf.org/doc/html/rfc9110#section-15.5.14", "description": "The server is refusing to process a request because the request content is larger than the server is willing or able to process.", "expectsEmptyBody": false, "cacheability": "uncacheable", "requiresAuth": false, "safeForMethods": [ "POST", "PUT", "PATCH" ], "relatedHeaders": [ { "name": "Retry-After", "required": false, "purpose": "Indicates when the condition may be temporary." } ], "aliases": [ "Payload Too Large", "Request Entity Too Large" ], "deprecated": false, "guidance": { "isRetryable": false, "retryStrategy": "never", "agentAction": "Reduce body size, chunk the upload, or use a different endpoint.", "commonCauses": [ "Upload exceeds server limit." ], "relatedStatuses": [] } }, "414": { "code": 414, "phrase": "URI Too Long", "category": "Client Error", "source": "IANA", "rfc": "RFC9110", "specUrl": "https://datatracker.ietf.org/doc/html/rfc9110#section-15.5.15", "description": "The server is refusing to service the request because the request-target is longer than the server is willing to interpret.", "expectsEmptyBody": false, "cacheability": "heuristic", "requiresAuth": false, "safeForMethods": "all", "relatedHeaders": [], "aliases": [ "Request-URI Too Long" ], "deprecated": false, "guidance": { "isRetryable": false, "retryStrategy": "never", "agentAction": "Shorten the URL; move parameters into a POST body.", "commonCauses": [ "Excessive query string", "Loop generating long redirect URI" ], "relatedStatuses": [] } }, "415": { "code": 415, "phrase": "Unsupported Media Type", "category": "Client Error", "source": "IANA", "rfc": "RFC9110", "specUrl": "https://datatracker.ietf.org/doc/html/rfc9110#section-15.5.16", "description": "The server is refusing to service the request because the content is in a format not supported by this method on the target resource.", "expectsEmptyBody": false, "cacheability": "uncacheable", "requiresAuth": false, "safeForMethods": [ "POST", "PUT", "PATCH" ], "relatedHeaders": [ { "name": "Accept", "required": false, "purpose": "Indicates supported response types." }, { "name": "Accept-Encoding", "required": false, "purpose": "Indicates supported encodings." } ], "aliases": [], "deprecated": false, "guidance": { "isRetryable": false, "retryStrategy": "never", "agentAction": "Set Content-Type to a supported value and retry.", "commonCauses": [ "Wrong Content-Type", "Unsupported encoding" ], "relatedStatuses": [ 406 ] } }, "416": { "code": 416, "phrase": "Range Not Satisfiable", "category": "Client Error", "source": "IANA", "rfc": "RFC9110", "specUrl": "https://datatracker.ietf.org/doc/html/rfc9110#section-15.5.17", "description": "None of the ranges in the request's Range header field overlap the current extent of the selected resource, or the set of ranges requested has been rejected.", "expectsEmptyBody": false, "cacheability": "uncacheable", "requiresAuth": false, "safeForMethods": [ "GET", "HEAD" ], "relatedHeaders": [ { "name": "Content-Range", "required": false, "purpose": "Total size of the representation." } ], "aliases": [], "deprecated": false, "guidance": { "isRetryable": false, "retryStrategy": "never", "agentAction": "Re-check the resource length and request a valid range.", "commonCauses": [ "Range beyond resource length." ], "relatedStatuses": [ 206 ] } }, "417": { "code": 417, "phrase": "Expectation Failed", "category": "Client Error", "source": "IANA", "rfc": "RFC9110", "specUrl": "https://datatracker.ietf.org/doc/html/rfc9110#section-15.5.18", "description": "The expectation given in the request's Expect header field could not be met by at least one of the inbound servers.", "expectsEmptyBody": false, "cacheability": "uncacheable", "requiresAuth": false, "safeForMethods": "all", "relatedHeaders": [], "aliases": [], "deprecated": false, "guidance": { "isRetryable": false, "retryStrategy": "never", "agentAction": "Remove the Expect header and retry.", "commonCauses": [ "Server does not support Expect: 100-continue." ], "relatedStatuses": [ 100 ] } }, "418": { "code": 418, "phrase": "I'm a teapot", "category": "Client Error", "source": "IANA", "rfc": "RFC2324", "specUrl": "https://datatracker.ietf.org/doc/html/rfc2324#section-2.3.2", "description": "Any attempt to brew coffee with a teapot should result in the error code 418 I'm a teapot. A joke status from the Hyper Text Coffee Pot Control Protocol.", "expectsEmptyBody": false, "cacheability": "uncacheable", "requiresAuth": false, "safeForMethods": "all", "relatedHeaders": [], "aliases": [], "deprecated": false, "guidance": { "isRetryable": false, "retryStrategy": "never", "agentAction": "Treat as a humorous easter egg or anti-bot signal; do not retry.", "commonCauses": [ "Server is signaling a refusal humorously." ], "relatedStatuses": [] } }, "421": { "code": 421, "phrase": "Misdirected Request", "category": "Client Error", "source": "IANA", "rfc": "RFC9110", "specUrl": "https://datatracker.ietf.org/doc/html/rfc9110#section-15.5.20", "description": "The request was directed at a server that is not able to produce a response. This can be sent by a server that is not configured to produce responses for the combination of scheme and authority included in the request URI.", "expectsEmptyBody": false, "cacheability": "uncacheable", "requiresAuth": false, "safeForMethods": "all", "relatedHeaders": [], "aliases": [], "deprecated": false, "guidance": { "isRetryable": true, "retryStrategy": "immediate", "agentAction": "Re-resolve the host and open a new connection before retrying.", "commonCauses": [ "HTTP/2 connection coalescing to wrong origin." ], "relatedStatuses": [] } }, "422": { "code": 422, "phrase": "Unprocessable Content", "category": "Client Error", "source": "IANA", "rfc": "RFC9110", "specUrl": "https://datatracker.ietf.org/doc/html/rfc9110#section-15.5.21", "description": "The server understands the content type of the request content and the syntax of the request content is correct, but it was unable to process the contained instructions.", "expectsEmptyBody": false, "cacheability": "uncacheable", "requiresAuth": false, "safeForMethods": "all", "relatedHeaders": [], "aliases": [ "Unprocessable Entity" ], "deprecated": false, "guidance": { "isRetryable": false, "retryStrategy": "never", "agentAction": "Validate semantic constraints (e.g., schema validation errors) and resubmit.", "commonCauses": [ "Schema validation failure", "Business rule violation" ], "relatedStatuses": [ 400 ] } }, "423": { "code": 423, "phrase": "Locked", "category": "Client Error", "source": "IANA", "rfc": "RFC4918", "specUrl": "https://datatracker.ietf.org/doc/html/rfc4918#section-11.3", "description": "WebDAV: the source or destination resource is locked.", "expectsEmptyBody": false, "cacheability": "uncacheable", "requiresAuth": false, "safeForMethods": "all", "relatedHeaders": [], "aliases": [], "deprecated": false, "guidance": { "isRetryable": true, "retryStrategy": "exponential-backoff", "agentAction": "Acquire the lock or wait for it to release, then retry.", "commonCauses": [ "WebDAV resource locked by another client." ], "relatedStatuses": [ 424 ] } }, "424": { "code": 424, "phrase": "Failed Dependency", "category": "Client Error", "source": "IANA", "rfc": "RFC4918", "specUrl": "https://datatracker.ietf.org/doc/html/rfc4918#section-11.4", "description": "WebDAV: the method could not be performed on the resource because the requested action depended on another action which failed.", "expectsEmptyBody": false, "cacheability": "uncacheable", "requiresAuth": false, "safeForMethods": "all", "relatedHeaders": [], "aliases": [], "deprecated": false, "guidance": { "isRetryable": false, "retryStrategy": "never", "agentAction": "Resolve the failing prerequisite action first.", "commonCauses": [ "Prior WebDAV operation in the same request failed." ], "relatedStatuses": [ 423 ] } }, "425": { "code": 425, "phrase": "Too Early", "category": "Client Error", "source": "IANA", "rfc": "RFC8470", "specUrl": "https://datatracker.ietf.org/doc/html/rfc8470#section-5.2", "description": "Indicates that the server is unwilling to risk processing a request that might be replayed (e.g., TLS 1.3 early data).", "expectsEmptyBody": false, "cacheability": "uncacheable", "requiresAuth": false, "safeForMethods": "all", "relatedHeaders": [ { "name": "Early-Data", "required": false, "purpose": "Indicates the request was sent in TLS early data." } ], "aliases": [], "deprecated": false, "guidance": { "isRetryable": true, "retryStrategy": "immediate", "agentAction": "Retry the request after the TLS handshake completes.", "commonCauses": [ "Request sent in TLS 1.3 0-RTT early data." ], "relatedStatuses": [] } }, "426": { "code": 426, "phrase": "Upgrade Required", "category": "Client Error", "source": "IANA", "rfc": "RFC9110", "specUrl": "https://datatracker.ietf.org/doc/html/rfc9110#section-15.5.22", "description": "The server refuses to perform the request using the current protocol but might be willing to do so after the client upgrades to a different protocol.", "expectsEmptyBody": false, "cacheability": "uncacheable", "requiresAuth": false, "safeForMethods": "all", "relatedHeaders": [ { "name": "Upgrade", "required": true, "purpose": "Protocols the server is willing to switch to." }, { "name": "Connection", "required": true, "purpose": "Must include \"Upgrade\"." } ], "aliases": [], "deprecated": false, "guidance": { "isRetryable": true, "retryStrategy": "immediate", "agentAction": "Upgrade to the protocol indicated in Upgrade and retry.", "commonCauses": [ "Server requires HTTPS or HTTP/2." ], "relatedStatuses": [ 101 ] } }, "428": { "code": 428, "phrase": "Precondition Required", "category": "Client Error", "source": "IANA", "rfc": "RFC6585", "specUrl": "https://datatracker.ietf.org/doc/html/rfc6585#section-3", "description": "The origin server requires the request to be conditional. Intended to prevent the lost update problem.", "expectsEmptyBody": false, "cacheability": "uncacheable", "requiresAuth": false, "safeForMethods": "all", "relatedHeaders": [], "aliases": [], "deprecated": false, "guidance": { "isRetryable": false, "retryStrategy": "never", "agentAction": "Add If-Match or If-Unmodified-Since and retry.", "commonCauses": [ "Server enforces optimistic concurrency control." ], "relatedStatuses": [ 412 ] } }, "429": { "code": 429, "phrase": "Too Many Requests", "category": "Client Error", "source": "IANA", "rfc": "RFC6585", "specUrl": "https://datatracker.ietf.org/doc/html/rfc6585#section-4", "description": "The user has sent too many requests in a given amount of time (\"rate limiting\").", "expectsEmptyBody": false, "cacheability": "uncacheable", "requiresAuth": false, "safeForMethods": "all", "relatedHeaders": [ { "name": "Retry-After", "required": false, "purpose": "Indicates how long to wait before retrying." } ], "aliases": [], "deprecated": false, "guidance": { "isRetryable": true, "retryStrategy": "respect-retry-after", "agentAction": "Wait the duration in Retry-After (or back off exponentially) and retry.", "commonCauses": [ "Rate limit exceeded." ], "relatedStatuses": [ 503, 509 ] } }, "431": { "code": 431, "phrase": "Request Header Fields Too Large", "category": "Client Error", "source": "IANA", "rfc": "RFC6585", "specUrl": "https://datatracker.ietf.org/doc/html/rfc6585#section-5", "description": "The server is unwilling to process the request because its header fields are too large.", "expectsEmptyBody": false, "cacheability": "uncacheable", "requiresAuth": false, "safeForMethods": "all", "relatedHeaders": [], "aliases": [], "deprecated": false, "guidance": { "isRetryable": false, "retryStrategy": "never", "agentAction": "Trim cookies/headers and retry.", "commonCauses": [ "Oversized cookie jar", "Long Authorization token" ], "relatedStatuses": [] } }, "444": { "code": 444, "phrase": "No Response", "category": "Vendor Extension", "source": "Nginx", "rfc": null, "specUrl": "https://nginx.org/en/docs/http/ngx_http_rewrite_module.html#return", "description": "Nginx-specific code instructing the server to close the connection without sending any response headers (used via \"return 444;\").", "expectsEmptyBody": true, "cacheability": "uncacheable", "requiresAuth": false, "safeForMethods": "all", "relatedHeaders": [], "aliases": [], "deprecated": false, "guidance": { "isRetryable": false, "retryStrategy": "never", "agentAction": "Treat as a deliberate drop; do not retry the same request.", "commonCauses": [ "Anti-abuse rule", "Malformed request blocked at the edge" ], "relatedStatuses": [] } }, "451": { "code": 451, "phrase": "Unavailable For Legal Reasons", "category": "Client Error", "source": "IANA", "rfc": "RFC7725", "specUrl": "https://datatracker.ietf.org/doc/html/rfc7725#section-3", "description": "The server is denying access to the resource as a consequence of a legal demand.", "expectsEmptyBody": false, "cacheability": "uncacheable", "requiresAuth": false, "safeForMethods": "all", "relatedHeaders": [], "aliases": [], "deprecated": false, "guidance": { "isRetryable": false, "retryStrategy": "never", "agentAction": "Surface the legal blockage to the user; do not retry.", "commonCauses": [ "Court order", "Government censorship", "DMCA takedown" ], "relatedStatuses": [ 403 ] } }, "494": { "code": 494, "phrase": "Request Header Too Large", "category": "Vendor Extension", "source": "Nginx", "rfc": null, "specUrl": "https://nginx.org/en/docs/http/ngx_http_core_module.html#large_client_header_buffers", "description": "Nginx-specific code returned when the request headers exceed large_client_header_buffers.", "expectsEmptyBody": false, "cacheability": "uncacheable", "requiresAuth": false, "safeForMethods": "all", "relatedHeaders": [], "aliases": [], "deprecated": false, "guidance": { "isRetryable": false, "retryStrategy": "never", "agentAction": "Trim headers/cookies and retry.", "commonCauses": [ "Oversized cookie jar", "Long Authorization header" ], "relatedStatuses": [ 431 ] } }, "495": { "code": 495, "phrase": "SSL Certificate Error", "category": "Vendor Extension", "source": "Nginx", "rfc": null, "specUrl": "https://nginx.org/en/docs/http/ngx_http_ssl_module.html#ssl_verify_client", "description": "Nginx-specific code returned when client certificate verification fails.", "expectsEmptyBody": false, "cacheability": "uncacheable", "requiresAuth": false, "safeForMethods": "all", "relatedHeaders": [], "aliases": [], "deprecated": false, "guidance": { "isRetryable": false, "retryStrategy": "never", "agentAction": "Provide a valid client certificate and retry.", "commonCauses": [ "Expired or untrusted client certificate." ], "relatedStatuses": [ 496 ] } }, "496": { "code": 496, "phrase": "SSL Certificate Required", "category": "Vendor Extension", "source": "Nginx", "rfc": null, "specUrl": "https://nginx.org/en/docs/http/ngx_http_ssl_module.html#ssl_verify_client", "description": "Nginx-specific code returned when a client certificate was required but not provided.", "expectsEmptyBody": false, "cacheability": "uncacheable", "requiresAuth": true, "safeForMethods": "all", "relatedHeaders": [], "aliases": [], "deprecated": false, "guidance": { "isRetryable": false, "retryStrategy": "never", "agentAction": "Attach a client certificate to the TLS connection and retry.", "commonCauses": [ "Mutual TLS endpoint reached without a client cert." ], "relatedStatuses": [ 495 ] } }, "497": { "code": 497, "phrase": "HTTP Request Sent to HTTPS Port", "category": "Vendor Extension", "source": "Nginx", "rfc": null, "specUrl": "https://nginx.org/en/docs/http/ngx_http_ssl_module.html#errors", "description": "Nginx-specific code returned when a plain HTTP request is sent to an HTTPS port.", "expectsEmptyBody": false, "cacheability": "uncacheable", "requiresAuth": false, "safeForMethods": "all", "relatedHeaders": [], "aliases": [], "deprecated": false, "guidance": { "isRetryable": true, "retryStrategy": "immediate", "agentAction": "Reissue the request over HTTPS.", "commonCauses": [ "Client used http:// against an https-only port." ], "relatedStatuses": [ 426 ] } }, "499": { "code": 499, "phrase": "Client Closed Request", "category": "Vendor Extension", "source": "Nginx", "rfc": null, "specUrl": "https://nginx.org/en/docs/http/ngx_http_core_module.html", "description": "Nginx-specific code logged when the client closes the connection while the server is still processing the request.", "expectsEmptyBody": true, "cacheability": "uncacheable", "requiresAuth": false, "safeForMethods": "all", "relatedHeaders": [], "aliases": [], "deprecated": false, "guidance": { "isRetryable": false, "retryStrategy": "never", "agentAction": "No action; this code is observed in access logs, not received by the client.", "commonCauses": [ "Client aborted the request", "Network drop" ], "relatedStatuses": [ 408 ] } }, "500": { "code": 500, "phrase": "Internal Server Error", "category": "Server Error", "source": "IANA", "rfc": "RFC9110", "specUrl": "https://datatracker.ietf.org/doc/html/rfc9110#section-15.6.1", "description": "The server encountered an unexpected condition that prevented it from fulfilling the request.", "expectsEmptyBody": false, "cacheability": "uncacheable", "requiresAuth": false, "safeForMethods": "all", "relatedHeaders": [], "aliases": [], "deprecated": false, "guidance": { "isRetryable": true, "retryStrategy": "exponential-backoff", "agentAction": "Retry idempotent requests with backoff; report to the operator if persistent.", "commonCauses": [ "Unhandled exception", "Database failure", "Misconfiguration" ], "relatedStatuses": [ 502, 503 ] } }, "501": { "code": 501, "phrase": "Not Implemented", "category": "Server Error", "source": "IANA", "rfc": "RFC9110", "specUrl": "https://datatracker.ietf.org/doc/html/rfc9110#section-15.6.2", "description": "The server does not support the functionality required to fulfill the request.", "expectsEmptyBody": false, "cacheability": "heuristic", "requiresAuth": false, "safeForMethods": "all", "relatedHeaders": [], "aliases": [], "deprecated": false, "guidance": { "isRetryable": false, "retryStrategy": "never", "agentAction": "Use a different method or endpoint; this feature is not supported.", "commonCauses": [ "Server lacks support for the requested method." ], "relatedStatuses": [ 405 ] } }, "502": { "code": 502, "phrase": "Bad Gateway", "category": "Server Error", "source": "IANA", "rfc": "RFC9110", "specUrl": "https://datatracker.ietf.org/doc/html/rfc9110#section-15.6.3", "description": "The server, while acting as a gateway or proxy, received an invalid response from an inbound server.", "expectsEmptyBody": false, "cacheability": "uncacheable", "requiresAuth": false, "safeForMethods": "all", "relatedHeaders": [], "aliases": [], "deprecated": false, "guidance": { "isRetryable": true, "retryStrategy": "exponential-backoff", "agentAction": "Retry with backoff; the upstream is likely transiently unhealthy.", "commonCauses": [ "Upstream returned malformed response", "Origin briefly down" ], "relatedStatuses": [ 503, 504 ] } }, "503": { "code": 503, "phrase": "Service Unavailable", "category": "Server Error", "source": "IANA", "rfc": "RFC9110", "specUrl": "https://datatracker.ietf.org/doc/html/rfc9110#section-15.6.4", "description": "The server is currently unable to handle the request due to a temporary overload or scheduled maintenance.", "expectsEmptyBody": false, "cacheability": "uncacheable", "requiresAuth": false, "safeForMethods": "all", "relatedHeaders": [ { "name": "Retry-After", "required": false, "purpose": "Indicates how long the service is expected to be unavailable." } ], "aliases": [], "deprecated": false, "guidance": { "isRetryable": true, "retryStrategy": "respect-retry-after", "agentAction": "Respect Retry-After if present; otherwise back off exponentially.", "commonCauses": [ "Overload", "Scheduled maintenance", "Circuit breaker open" ], "relatedStatuses": [ 429, 502, 504 ] } }, "504": { "code": 504, "phrase": "Gateway Timeout", "category": "Server Error", "source": "IANA", "rfc": "RFC9110", "specUrl": "https://datatracker.ietf.org/doc/html/rfc9110#section-15.6.5", "description": "The server, while acting as a gateway or proxy, did not receive a timely response from an upstream server.", "expectsEmptyBody": false, "cacheability": "uncacheable", "requiresAuth": false, "safeForMethods": "all", "relatedHeaders": [], "aliases": [], "deprecated": false, "guidance": { "isRetryable": true, "retryStrategy": "exponential-backoff", "agentAction": "Retry with backoff; consider increasing the upstream timeout.", "commonCauses": [ "Slow upstream", "Network partition" ], "relatedStatuses": [ 408, 502 ] } }, "505": { "code": 505, "phrase": "HTTP Version Not Supported", "category": "Server Error", "source": "IANA", "rfc": "RFC9110", "specUrl": "https://datatracker.ietf.org/doc/html/rfc9110#section-15.6.6", "description": "The server does not support, or refuses to support, the major version of HTTP that was used in the request.", "expectsEmptyBody": false, "cacheability": "uncacheable", "requiresAuth": false, "safeForMethods": "all", "relatedHeaders": [], "aliases": [], "deprecated": false, "guidance": { "isRetryable": false, "retryStrategy": "never", "agentAction": "Downgrade or upgrade to a supported HTTP version and retry.", "commonCauses": [ "Client speaks HTTP version the server has disabled." ], "relatedStatuses": [ 426 ] } }, "506": { "code": 506, "phrase": "Variant Also Negotiates", "category": "Server Error", "source": "IANA", "rfc": "RFC2295", "specUrl": "https://datatracker.ietf.org/doc/html/rfc2295#section-8.1", "description": "Transparent content negotiation for the request results in a circular reference.", "expectsEmptyBody": false, "cacheability": "uncacheable", "requiresAuth": false, "safeForMethods": "all", "relatedHeaders": [], "aliases": [], "deprecated": false, "guidance": { "isRetryable": false, "retryStrategy": "never", "agentAction": "Server-side configuration bug; report to the operator.", "commonCauses": [ "Misconfigured content negotiation chain." ], "relatedStatuses": [] } }, "507": { "code": 507, "phrase": "Insufficient Storage", "category": "Server Error", "source": "IANA", "rfc": "RFC4918", "specUrl": "https://datatracker.ietf.org/doc/html/rfc4918#section-11.5", "description": "WebDAV: the method could not be performed on the resource because the server is unable to store the representation needed to successfully complete the request.", "expectsEmptyBody": false, "cacheability": "uncacheable", "requiresAuth": false, "safeForMethods": "all", "relatedHeaders": [], "aliases": [], "deprecated": false, "guidance": { "isRetryable": true, "retryStrategy": "exponential-backoff", "agentAction": "Retry later or reduce payload size; storage is full upstream.", "commonCauses": [ "Disk full on server." ], "relatedStatuses": [ 413 ] } }, "508": { "code": 508, "phrase": "Loop Detected", "category": "Server Error", "source": "IANA", "rfc": "RFC5842", "specUrl": "https://datatracker.ietf.org/doc/html/rfc5842#section-7.2", "description": "WebDAV: the server terminated an operation because it encountered an infinite loop while processing a request with Depth: infinity.", "expectsEmptyBody": false, "cacheability": "uncacheable", "requiresAuth": false, "safeForMethods": "all", "relatedHeaders": [], "aliases": [], "deprecated": false, "guidance": { "isRetryable": false, "retryStrategy": "never", "agentAction": "Restructure the request to avoid the cycle.", "commonCauses": [ "Cyclic WebDAV bindings." ], "relatedStatuses": [] } }, "510": { "code": 510, "phrase": "Not Extended", "category": "Server Error", "source": "IANA", "rfc": "RFC2774", "specUrl": "https://datatracker.ietf.org/doc/html/rfc2774#section-7", "description": "Further extensions to the request are required for the server to fulfill it.", "expectsEmptyBody": false, "cacheability": "uncacheable", "requiresAuth": false, "safeForMethods": "all", "relatedHeaders": [], "aliases": [], "deprecated": true, "guidance": { "isRetryable": false, "retryStrategy": "never", "agentAction": "Add the required HTTP extension declarations and retry.", "commonCauses": [ "Server requires HTTP extension framework." ], "relatedStatuses": [] } }, "511": { "code": 511, "phrase": "Network Authentication Required", "category": "Server Error", "source": "IANA", "rfc": "RFC6585", "specUrl": "https://datatracker.ietf.org/doc/html/rfc6585#section-6", "description": "The client needs to authenticate to gain network access. Intended for captive portals.", "expectsEmptyBody": false, "cacheability": "uncacheable", "requiresAuth": true, "safeForMethods": "all", "relatedHeaders": [], "aliases": [], "deprecated": false, "guidance": { "isRetryable": true, "retryStrategy": "immediate", "agentAction": "Complete the captive portal flow, then retry.", "commonCauses": [ "Public Wi-Fi captive portal." ], "relatedStatuses": [ 401 ] } }, "520": { "code": 520, "phrase": "Web Server Returned an Unknown Error", "category": "Vendor Extension", "source": "Cloudflare", "rfc": null, "specUrl": "https://developers.cloudflare.com/support/troubleshooting/http-status-codes/5xx-errors/#error-520-web-server-returns-an-unknown-error", "description": "The origin server returned an empty, unknown, or unexpected response to Cloudflare.", "expectsEmptyBody": false, "cacheability": "uncacheable", "requiresAuth": false, "safeForMethods": "all", "relatedHeaders": [], "aliases": [], "deprecated": false, "guidance": { "isRetryable": true, "retryStrategy": "exponential-backoff", "agentAction": "Retry; if persistent, the origin is misbehaving and needs operator attention.", "commonCauses": [ "Origin crashed mid-response", "Origin returned malformed HTTP" ], "relatedStatuses": [ 502 ] } }, "521": { "code": 521, "phrase": "Web Server Is Down", "category": "Vendor Extension", "source": "Cloudflare", "rfc": null, "specUrl": "https://developers.cloudflare.com/support/troubleshooting/http-status-codes/5xx-errors/#error-521-web-server-is-down", "description": "The origin server refused the connection from Cloudflare. Cloudflare could not establish a TCP connection.", "expectsEmptyBody": false, "cacheability": "uncacheable", "requiresAuth": false, "safeForMethods": "all", "relatedHeaders": [], "aliases": [], "deprecated": false, "guidance": { "isRetryable": true, "retryStrategy": "exponential-backoff", "agentAction": "Retry; verify origin is running and not blocking Cloudflare IPs.", "commonCauses": [ "Origin down", "Cloudflare IPs blocked at firewall" ], "relatedStatuses": [ 502, 503 ] } }, "522": { "code": 522, "phrase": "Connection Timed Out", "category": "Vendor Extension", "source": "Cloudflare", "rfc": null, "specUrl": "https://developers.cloudflare.com/support/troubleshooting/http-status-codes/5xx-errors/#error-522-connection-timed-out", "description": "Cloudflare could not negotiate a TCP handshake with the origin server before timing out.", "expectsEmptyBody": false, "cacheability": "uncacheable", "requiresAuth": false, "safeForMethods": "all", "relatedHeaders": [], "aliases": [], "deprecated": false, "guidance": { "isRetryable": true, "retryStrategy": "exponential-backoff", "agentAction": "Retry; investigate origin network reachability.", "commonCauses": [ "Origin overloaded", "Network partition between CF and origin" ], "relatedStatuses": [ 504 ] } }, "523": { "code": 523, "phrase": "Origin Is Unreachable", "category": "Vendor Extension", "source": "Cloudflare", "rfc": null, "specUrl": "https://developers.cloudflare.com/support/troubleshooting/http-status-codes/5xx-errors/#error-523-origin-is-unreachable", "description": "Cloudflare could not reach the origin server, commonly due to a routing/BGP issue or invalid DNS record.", "expectsEmptyBody": false, "cacheability": "uncacheable", "requiresAuth": false, "safeForMethods": "all", "relatedHeaders": [], "aliases": [], "deprecated": false, "guidance": { "isRetryable": true, "retryStrategy": "exponential-backoff", "agentAction": "Retry; if persistent, check origin DNS and routing.", "commonCauses": [ "DNS record points to wrong IP", "BGP routing problem" ], "relatedStatuses": [ 530 ] } }, "524": { "code": 524, "phrase": "A Timeout Occurred", "category": "Vendor Extension", "source": "Cloudflare", "rfc": null, "specUrl": "https://developers.cloudflare.com/support/troubleshooting/http-status-codes/5xx-errors/#error-524-a-timeout-occurred", "description": "Cloudflare successfully connected and sent data to the origin, but the origin took too long to respond with an HTTP response.", "expectsEmptyBody": false, "cacheability": "uncacheable", "requiresAuth": false, "safeForMethods": "all", "relatedHeaders": [], "aliases": [], "deprecated": false, "guidance": { "isRetryable": true, "retryStrategy": "exponential-backoff", "agentAction": "Retry; for long-running requests, consider an async pattern (e.g., 202 + polling).", "commonCauses": [ "Long-running origin request exceeded the 100-second CF limit." ], "relatedStatuses": [ 504, 408 ] } }, "525": { "code": 525, "phrase": "SSL Handshake Failed", "category": "Vendor Extension", "source": "Cloudflare", "rfc": null, "specUrl": "https://developers.cloudflare.com/support/troubleshooting/http-status-codes/5xx-errors/#error-525-ssl-handshake-failed", "description": "Cloudflare could not negotiate an SSL/TLS handshake with the origin server.", "expectsEmptyBody": false, "cacheability": "uncacheable", "requiresAuth": false, "safeForMethods": "all", "relatedHeaders": [], "aliases": [], "deprecated": false, "guidance": { "isRetryable": false, "retryStrategy": "never", "agentAction": "Operator action: align cipher suites and TLS versions between CF and origin.", "commonCauses": [ "No common cipher suite", "TLS version mismatch" ], "relatedStatuses": [ 526 ] } }, "526": { "code": 526, "phrase": "Invalid SSL Certificate", "category": "Vendor Extension", "source": "Cloudflare", "rfc": null, "specUrl": "https://developers.cloudflare.com/support/troubleshooting/http-status-codes/5xx-errors/#error-526-invalid-ssl-certificate", "description": "Cloudflare could not validate the SSL certificate on the origin web server when SSL Full (strict) mode is active.", "expectsEmptyBody": false, "cacheability": "uncacheable", "requiresAuth": false, "safeForMethods": "all", "relatedHeaders": [], "aliases": [], "deprecated": false, "guidance": { "isRetryable": false, "retryStrategy": "never", "agentAction": "Operator action: install a valid origin certificate or relax SSL mode.", "commonCauses": [ "Expired or self-signed origin cert", "Hostname mismatch" ], "relatedStatuses": [ 525 ] } }, "527": { "code": 527, "phrase": "Railgun Error", "category": "Vendor Extension", "source": "Cloudflare", "rfc": null, "specUrl": "https://developers.cloudflare.com/support/troubleshooting/http-status-codes/5xx-errors/#error-527-railgun-listener-to-origin", "description": "Indicates an error connecting between Cloudflare and the origin's Railgun (rwengine) server.", "expectsEmptyBody": false, "cacheability": "uncacheable", "requiresAuth": false, "safeForMethods": "all", "relatedHeaders": [], "aliases": [], "deprecated": true, "guidance": { "isRetryable": true, "retryStrategy": "exponential-backoff", "agentAction": "Retry; Railgun is largely deprecated in favor of Argo Smart Routing.", "commonCauses": [ "Railgun listener unreachable." ], "relatedStatuses": [] } }, "530": { "code": 530, "phrase": "Origin DNS Error", "category": "Vendor Extension", "source": "Cloudflare", "rfc": null, "specUrl": "https://developers.cloudflare.com/support/troubleshooting/cloudflare-errors/troubleshooting-cloudflare-1xxx-errors/", "description": "A 530 response is typically returned alongside a Cloudflare 1xxx error displayed in the body, indicating an origin DNS or worker failure.", "expectsEmptyBody": false, "cacheability": "uncacheable", "requiresAuth": false, "safeForMethods": "all", "relatedHeaders": [], "aliases": [], "deprecated": false, "guidance": { "isRetryable": true, "retryStrategy": "exponential-backoff", "agentAction": "Inspect the body for the embedded 1xxx code; resolve DNS or Worker error.", "commonCauses": [ "Origin DNS resolution failure", "Worker script error" ], "relatedStatuses": [ 523 ] } } }