📖 Guide

HTTP Status Codes — Complete Reference

Every standard HTTP status code with descriptions, use cases, and common patterns for web developers.

72 commands across 6 categories

1xx Informational 2xx Success 3xx Redirection 4xx Client Error 5xx Server Error Common Patterns

1xx Informational

Command	Description
`100 Continue`	Server received request headers; client should proceed to send the body
`101 Switching Protocols`	Server is switching protocols as requested by the client (e.g., to WebSocket)
`102 Processing`	Server has received and is processing the request, but no response is available yet (WebDAV)
`103 Early Hints`	Used to return some response headers before final HTTP message, allowing preloading of resources

2xx Success

Command	Description
`200 OK`	Standard success response. Body contains the requested resource
`201 Created` e.g. POST /api/users -> 201 with Location header	Request succeeded and a new resource was created. Typically returned after POST/PUT
`202 Accepted`	Request accepted for processing, but processing is not yet complete (async operations)
`203 Non-Authoritative Information`	Response from a transforming proxy; metadata differs from origin server
`204 No Content` e.g. DELETE /api/users/123 -> 204	Request succeeded but no body returned. Common for DELETE or PUT responses
`205 Reset Content`	Request succeeded; client should reset the document view (e.g., clear a form)
`206 Partial Content` e.g. Range: bytes=0-1023 -> 206 with Content-Range header	Server is delivering part of the resource due to a Range header
`207 Multi-Status`	Conveys information about multiple resources where multiple status codes might be appropriate (WebDAV)
`208 Already Reported`	Members of a DAV binding have already been enumerated and are not included again (WebDAV)
`226 IM Used`	Server has fulfilled a GET request with instance-manipulations applied to the current instance

3xx Redirection

Command	Description
`300 Multiple Choices`	Multiple possible responses; user or user agent should choose one
`301 Moved Permanently` e.g. Location: https://new-domain.com/page	Resource has been permanently moved to a new URL. Search engines update their links
`302 Found`	Resource temporarily at a different URI. Client should continue using the original URI for future requests
`303 See Other`	Server redirects to a different resource via GET, typically after a POST operation
`304 Not Modified` e.g. If-None-Match: "etag" -> 304 (use cached version)	Resource has not been modified since last request. Used with caching headers (ETag, If-Modified-Since)
`305 Use Proxy`	Requested resource must be accessed through the proxy in the Location header (deprecated)
`307 Temporary Redirect`	Like 302 but guarantees the HTTP method will NOT change (POST stays POST)
`308 Permanent Redirect`	Like 301 but guarantees the HTTP method will NOT change (POST stays POST)

4xx Client Error

Command	Description
`400 Bad Request`	Server cannot process the request due to malformed syntax, invalid framing, or deceptive routing
`401 Unauthorized`	Authentication is required and has failed or not been provided. Include WWW-Authenticate header
`402 Payment Required`	Reserved for future use. Sometimes used for paywalled content or API rate limiting
`403 Forbidden`	Server understood the request but refuses to authorize it. Authentication won't help
`404 Not Found`	Requested resource could not be found on the server
`405 Method Not Allowed` e.g. Allow: GET, POST	HTTP method is not supported for the requested resource. Must include Allow header
`406 Not Acceptable`	Server cannot produce a response matching the Accept headers sent by the client
`407 Proxy Authentication Required`	Client must first authenticate itself with the proxy
`408 Request Timeout`	Server timed out waiting for the request from the client
`409 Conflict` e.g. POST /users with duplicate email -> 409	Request conflicts with the current state of the resource (e.g., edit conflicts, duplicate entries)
`410 Gone`	Resource is permanently gone and will not be available again. Unlike 404, this is intentional
`411 Length Required`	Server requires a Content-Length header in the request
`412 Precondition Failed`	One or more conditions in the request headers evaluated to false (e.g., If-Match)
`413 Content Too Large`	Request body is larger than the server is willing to process
`414 URI Too Long`	URI provided was too long for the server to process
`415 Unsupported Media Type` e.g. Sending XML when only JSON is accepted -> 415	Server does not support the media type of the request body
`416 Range Not Satisfiable`	Range specified in the Range header cannot be fulfilled
`417 Expectation Failed`	Server cannot meet the requirements of the Expect request header
`418 I'm a Teapot`	Returned by teapots asked to brew coffee (RFC 2324). Used humorously as an Easter egg
`421 Misdirected Request`	Request was directed at a server that cannot produce a response
`422 Unprocessable Content` e.g. POST /users with invalid email format -> 422	Request was well-formed but contained semantic errors (e.g., validation failures)
`423 Locked`	Resource being accessed is locked (WebDAV)
`424 Failed Dependency`	Request failed because it depended on another request that failed (WebDAV)
`425 Too Early`	Server unwilling to process a request that might be replayed (TLS Early Data)
`426 Upgrade Required`	Server refuses the request using the current protocol; client must upgrade (e.g., to TLS)
`428 Precondition Required`	Server requires the request to be conditional (e.g., include If-Match header)
`429 Too Many Requests` e.g. Retry-After: 60	Client has sent too many requests in a given time period (rate limiting)
`431 Request Header Fields Too Large`	Server refuses the request because headers are too large
`451 Unavailable For Legal Reasons`	Resource is unavailable due to legal demands (censorship, court order)

5xx Server Error

Command	Description
`500 Internal Server Error`	Generic server error when no more specific message is suitable
`501 Not Implemented`	Server does not support the functionality required to fulfill the request
`502 Bad Gateway`	Server acting as a gateway received an invalid response from the upstream server
`503 Service Unavailable` e.g. Retry-After: 120	Server is currently unable to handle the request (overloaded or under maintenance)
`504 Gateway Timeout`	Server acting as a gateway did not receive a timely response from the upstream server
`505 HTTP Version Not Supported`	Server does not support the HTTP version used in the request
`506 Variant Also Negotiates`	Transparent content negotiation results in a circular reference
`507 Insufficient Storage`	Server is unable to store the representation needed to complete the request (WebDAV)
`508 Loop Detected`	Server detected an infinite loop while processing the request (WebDAV)
`510 Not Extended`	Further extensions to the request are required for the server to fulfill it
`511 Network Authentication Required`	Client needs to authenticate to gain network access (captive portals)

Common Patterns

Command	Description
`REST: GET -> 200`	Successful resource retrieval
`REST: POST -> 201`	Successful resource creation with Location header
`REST: PUT -> 200 or 204`	Successful update (200 with body, 204 without)
`REST: DELETE -> 204`	Successful deletion, no body returned
`Auth: 401 vs 403`	401 = not logged in (can retry with credentials). 403 = logged in but not authorized (retrying won't help)
`Redirect: 301 vs 308`	Both permanent. 301 may change POST to GET. 308 preserves the HTTP method
`Redirect: 302 vs 307`	Both temporary. 302 may change POST to GET. 307 preserves the HTTP method
`Validation: 400 vs 422`	400 = malformed request (bad JSON). 422 = well-formed but semantically invalid (failed validation)
`Caching: ETag + 304`	Client sends If-None-Match with ETag. Server returns 304 if unchanged, saving bandwidth
`Rate Limiting: 429 + Retry-After`	Always include Retry-After header to tell clients when to retry