HTTP status codes

Articles

• Where your 5xx class error comes from

  Reference guide

  5xx error family meaning, which server layer returns 500, 502, 503, 504 and 599, and how to react to each one.

• HTTP 102 Processing status explained

  Reference guide

  HTTP 102 Processing is an informational status once used to prevent WebDAV request timeouts while a request was being processed. Learn when 102 applies today.

• HTTP 207 multi status explained

  Reference guide

  HTTP 207 Multi-Status explained: when a batch request returns many statuses, how the WebDAV body works, and how to handle it as a client.

• HTTP 208 Already Reported (WebDAV) explained

  Reference guide

  Understand HTTP 208 Already Reported, the WebDAV binding status, and why it matters within PROPFIND responses.

• HTTP 300 Multiple Choices explained

  Reference guide

  Understand HTTP 300 Multiple Choices, its Location header role, and why modern servers prefer explicit redirects like 301 or 302.

• HTTP 301 redirects that preserve rankings

  Troubleshooting guide

  HTTP 301 redirect guide: when a 301 preserves rankings, how to write the server rule, and how to verify old URLs resolve to the new page.

• HTTP 302 and temporary redirects

  Reference guide

  HTTP 302 temporary redirect explained: when 302 is correct, when to choose 301 instead, and how to keep a temporary swap from becoming a SEO data leak.

• HTTP 304 Not Modified explained

  Reference guide

  Understand HTTP 304 Not Modified: how conditional requests with ETag and If-None-Match skip re-downloads and speed up repeat visits.

• HTTP 307 temporary redirect

  Reference guide

  HTTP 307 temporary redirect explained: it preserves the method and body, where it beats 302, and how to configure and test it.

• HTTP 308 permanent redirect

  Reference guide

  HTTP 308 permanent redirect: the method-preserving permanent status, when to choose it over 301, and how to configure it safely.

• HTTP 400 bad request

  Reference guide

  HTTP 400 bad request explained: causes from malformed syntax to oversized headers and cookie bombs, with an ordered fix list and a quick error table.

• HTTP 401 unauthorized explained

  Reference guide

  HTTP 401 unauthorized explained: the status means authentication failed, not authorization. How 401 differs from 403 and how clients, servers and security tools behave.

• HTTP 402 Payment Required explained

  Reference guide

  HTTP 402 status is reserved for payment-required responses but not defined by RFC; see how APIs and payment protocols use it.

• HTTP 403 forbidden

  Troubleshooting guide

  HTTP 403 forbidden guide: permissions, .htaccess rules, WAF false positives, index files and IP blocks, with an ordered fix sequence and prevention.

• HTTP 404 not found

  Troubleshooting guide

  What an HTTP 404 means, how to tell a real 404 from a soft 404, and how to fix dead URLs with redirects, correct status codes and a clean sitemap.

• HTTP 405 method not allowed

  Troubleshooting guide

  HTTP 405 method not allowed meaning and fix, from Allow header fingerprinting to route and server enforcement.

• HTTP 407 Proxy Authentication Required explained

  Troubleshooting guide

  Fix HTTP 407 Proxy Authentication Required: set proxy credentials, Proxy-Authenticate, and check captive or corporate proxy interception.

• HTTP 408 request timeout error

  Troubleshooting guide

  HTTP 408 request timeout means the server stopped waiting for a request. Diagnose client timeouts, proxies and retry behaviour.

• HTTP 409 conflict

  Reference guide

  HTTP 409 conflict meaning for concurrent writes and versioned APIs, with conditional request patterns and the right client response.

• HTTP 410 gone and permanent removal

  Reference guide

  HTTP 410 gone explained: the permanent removal signal, why it beats 404 for dead content, and how to return 410 for deleted pages on Apache, nginx and WordPress.

• HTTP 411 Length Required explained

  Troubleshooting guide

  Understand the HTTP 411 Length Required status, why Content-Length is needed, and how to fix the request.

• HTTP 412 precondition failed

  Troubleshooting guide

  HTTP 412 precondition failed occurs when If-Match or If-Unmodified-Since conditions fail. Refetch the resource and retry with a fresh validator.

• HTTP 413 payload too large error

  Troubleshooting guide

  HTTP 413 means the request body is too big: check nginx and Apache client limits, PHP upload values, proxies and the reading of the error log line.

• HTTP 415 Unsupported Media Type explained

  Troubleshooting guide

  Fix HTTP 415: check the request Content-Type, Accept expectations, and Content-Range upload handling when a server rejects a payload.

• HTTP 416 Range Not Satisfiable explained

  Reference guide

  HTTP 416 Range Not Satisfiable means the requested byte range does not overlap the resource. Learn what causes it and how to respond correctly.

• HTTP 417 Expectation Failed explained

  Reference guide

  HTTP 417 Expectation Failed means the server cannot meet the clients Expect request-header expectation. Learn what causes 417 and how to disable it.

• HTTP 421 Misdirected Request explained

  Troubleshooting guide

  Fix HTTP 421 Misdirected Request, an early 421 upgrade-time status, by aligning the Host header and connection with the intended target.

• HTTP 425 Too Early explained

  Reference guide

  Understand HTTP 425 Too Early, the RFC 8470 early data status, its causes with TLS 1.3 0-RTT, and how to handle it.

• HTTP 428 Precondition Required explained

  Reference guide

  HTTP 428 Precondition Required tells a client its request must include a precondition header to prevent a race. Learn when servers use 428 and how clients should respond.

• HTTP 429 too many requests

  Troubleshooting guide

  HTTP 429 too many requests: what triggers it, how Retry-After works, and the ordered steps to fix rate limits in APIs, WordPress and Cloudflare.

• HTTP 431 request header fields too large

  Troubleshooting guide

  HTTP 431 means request headers are too large, often from cookies or auth tokens. Reduce header size or raise the server limit.

• HTTP 451 unavailable for legal reasons

  Reference guide

  HTTP 451 unavailable for legal reasons meaning, RFC 7725 Link header, and how it differs from 403 and 404 in practice.

• HTTP 500 internal server error

  Troubleshooting guide

  Why a server returns 500 Internal Server Error, the ordered fix sequence (logs, restart, isolation, permissions, .htaccess, resource limits), and prevention.

• HTTP 501 Not Implemented troubleshooting

  Troubleshooting guide

  Diagnose and fix HTTP 501 Not Implemented responses, where a server rejects methods or features it does not support.

• HTTP 502 bad gateway

  Troubleshooting guide

  HTTP 502 bad gateway guide: cause chain from PHP-FPM crashes to origin timeouts, the ordered fix list, and how to verify the origin after a 502.

• HTTP 503 from a load balancer during origin drain

  Reference guide

  503 during a load-balancer origin drain: warm the unhealthy origin, drop it from the pool, route health checks and keep clients retrying correctly.

• HTTP 503 service unavailable

  Troubleshooting guide

  HTTP 503 service unavailable explained: the maintenance and overload status, examples with Retry-After, and the ordered fixing sequence.

• HTTP 504 gateway timeout

  Troubleshooting guide

  HTTP 504 gateway timeout: what the proxy is waiting for, how to read the logs for the upstream, and how to fix the slow request.

• HTTP 505 HTTP version not supported

  Troubleshooting guide

  HTTP 505 means the request used an HTTP version the server does not support. Diagnose request-line and upstream version mismatches.

• HTTP 508 Loop Detected explained

  Reference guide

  HTTP 508 Loop Detected explained: WebDAV request loops, when the code is served, and how to stop the recursion.

• HTTP 511 Network Authentication Required explained

  Reference guide

  HTTP 511 Network Authentication Required explained: who returns it, how captive portals work, and how clients should respond.

• HTTP status codes explained

  Reference guide

  HTTP status codes explained: the 1xx to 5xx classes, a quick reference table of common statuses, and how status codes interact with caching and redirects.

• Retry-After header explained

  Reference guide

  Retry-After header explained: delta-seconds vs date form, how 429 and 503 use it, and how clients retry without hammering the server.

• Unused and reserved HTTP status codes (306, 418)

  Reference guide

  Why HTTP status codes like 306 and 418 are reserved and unused, and what to do if you encounter them.