HTTP Status Code Reference

The client should continue sending the request body.

Troubleshoot: Waiting on 100-continue can time out; drop the Expect header and send the body.

The server agrees to switch protocols (e.g. WebSocket upgrade).

Troubleshoot: If the upgrade fails, check that the proxy forwards Upgrade and Connection headers.

Request received, still being processed.

Preliminary headers returned before the final response.

Troubleshoot: Not visible in DevTools is normal; check whether the CDN returned a response early.

The request succeeded.

The request succeeded and created a new resource.

Request accepted, not yet processed.

Troubleshoot: Accepted is not finished; poll the job status endpoint for the result.

Information returned from a non-authoritative copy.

Success with no response body.

Troubleshoot: Never send a body with 204; clients and proxies treat it as a protocol error.

Success; the client should reset the view.

Partial content returned (Range request).

Troubleshoot: If resumable downloads fail, check Accept-Ranges and Range handling.

Multiple statuses (WebDAV).

Troubleshoot: For WebDAV, parse the per-resource status codes in the XML body.

The resource has multiple representations.

The resource has permanently moved to a new URL.

Troubleshoot: Watch for redirect loops; browsers cache 301 long-term, so a bad one sticks.

The resource has temporarily moved.

Troubleshoot: Do not use 302 for permanent moves; switch to 301 or 308.

Retrieve another URI with GET.

Troubleshoot: After a form post, redirect with 303 to avoid resubmission on refresh.

The cached copy is still valid.

Troubleshoot: Stale content usually means ETag or Last-Modified disagree across servers.

Temporary redirect preserving the request method.

Troubleshoot: If POST turns into GET you picked the wrong code; 307 preserves the method.

Permanent redirect preserving the request method.

Troubleshoot: A permanent redirect that keeps the method; also cached long-term if wrong.

Malformed request syntax.

Troubleshoot: Check that the body parses and that Content-Type matches the actual format.

Authentication is required.

Troubleshoot: Check that credentials are sent and match the WWW-Authenticate scheme.

Payment required (reserved).

Authenticated but access is denied.

Troubleshoot: Separate genuine permission errors from WAF or Nginx deny rules, which also return 403.

The requested resource was not found.

Troubleshoot: Static 404s point to build output paths; API 404s to the route prefix.

The HTTP method is not allowed.

Troubleshoot: Read the Allow header; static servers often answer 405 to PUT or DELETE.

Cannot satisfy the Accept header.

Troubleshoot: Check Accept and Accept-Language against what the server can produce.

Proxy authentication is required.

Troubleshoot: Proxy auth failure: check Proxy-Authorization and the proxy configuration.

The client request timed out.

Troubleshoot: Large uploads timing out: raise client_body_timeout and keepalive_timeout.

The request conflicts with the resource state.

Troubleshoot: Concurrent write conflict; retry with optimistic locking or an idempotency key.

The resource has been permanently removed.

Troubleshoot: Only return 410 for genuinely retired URLs, then clean links and sitemaps.

Missing Content-Length header.

Troubleshoot: Add Content-Length, but never hand-write it when using chunked encoding.

A precondition header check failed.

Troubleshoot: Compare If-Match and If-Unmodified-Since with the current ETag.

The request body is too large.

Troubleshoot: Raise client_max_body_size and the gateway request body limit.

The request URI is too long.

Troubleshoot: Shorten the query string or use POST; runaway length usually means redirects appending params.

Unsupported media type.

Troubleshoot: Send the right Content-Type; a mismatched charset triggers this too.

The requested range is not satisfiable.

Troubleshoot: Check whether the Range exceeds the actual resource length.

The Expect header requirement failed.

Troubleshoot: The server ignores Expect; drop the header and retry.

Easter egg: I'm a teapot.

The request was sent to a server that cannot respond.

Troubleshoot: Check for SNI and HTTP version mismatches and the CDN origin host.

Syntactically valid but semantically wrong (e.g. form validation).

Troubleshoot: A validation failure; read the field-level errors in the response body.

The request is too early (replay risk).

Troubleshoot: TLS 1.3 early-data replay protection; just retry later.

A protocol upgrade is required (e.g. TLS).

Troubleshoot: When HTTPS or a protocol upgrade is enforced, check Upgrade and TLS config.

A precondition header is required.

Troubleshoot: The client must send a precondition header such as If-Match.

Too many requests (rate limited).

Troubleshoot: Read Retry-After and review rate limits such as limit_req or gateway QPS.

Request header fields are too large.

Troubleshoot: Trim cookies and custom headers, or raise large_client_header_buffers.

Unavailable for legal reasons.

Troubleshoot: Blocked by legal or regional policy; review compliance and geo rules.

Nginx extension: request header too large.

Troubleshoot: Raise large_client_header_buffers, or trim cookies and custom headers.

Nginx extension: client certificate failed verification.

Troubleshoot: Check ssl_verify_client and whether the client certificate chain is complete.

Nginx extension: client certificate required but not sent.

Troubleshoot: For mutual TLS, confirm the client is configured to send its certificate.

Nginx extension: HTTP request sent to an HTTPS port.

Troubleshoot: Use https instead, or add error_page 497 to redirect to https.

Nginx extension: the client closed the connection before the response.

Troubleshoot: Usually the backend was too slow; check upstream latency and timeout settings.

Internal server error.

Troubleshoot: Read the application log first, then the upstream section of the error log.

The requested functionality is not implemented.

Troubleshoot: Check whether the feature is implemented or the method is exposed.

The gateway received an invalid upstream response.

Troubleshoot: Check upstream liveness, port mapping, and connection pool saturation.

Service temporarily unavailable (overloaded or maintenance).

Troubleshoot: Check backend health, rate limiting and circuit breaker state, and maintenance mode.

The gateway timed out waiting for upstream.

Troubleshoot: Check proxy_read_timeout and slow queries on the backend.

The HTTP version is not supported.

Troubleshoot: Check the client HTTP version and protocol negotiation settings.

Insufficient storage (WebDAV).

Troubleshoot: Storage or quota exhausted; free space or expand the quota.

An infinite loop was detected (WebDAV).

Troubleshoot: A WebDAV loop; look for symlinks and rewrite rules.

Network authentication required (e.g. captive portal).

Troubleshoot: A captive portal login is required; verify the portal page loads.

Cloudflare extension: origin returned an empty or unknown response.

Troubleshoot: Compare origin access and fetch logs to see whether the origin returned nothing.

Cloudflare extension: the origin web server is down.

Troubleshoot: Verify the origin process and listening port, then check for a restart.

Cloudflare extension: connection to origin timed out.

Troubleshoot: Whitelist CDN egress IPs on the origin firewall and check network reachability.

Cloudflare extension: the origin is unreachable.

Troubleshoot: Check the origin address and DNS record, and whether the origin only listens internally.

Cloudflare extension: origin response timed out (100 s default).

Troubleshoot: Make long tasks asynchronous or cache them, and check origin-side slow queries.

Cloudflare extension: SSL handshake with the origin failed.

Troubleshoot: Check the origin certificate, TLS versions, and cipher suites supported by the CDN.

Cloudflare extension: the origin certificate is invalid.

Troubleshoot: Check the certificate chain and hostname match, or relax the SSL mode.

Cloudflare extension: Railgun listener error; the feature is retired.

Troubleshoot: Railgun has been retired; this is a legacy code and can be ignored.