📖 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 Informational2xx Success3xx Redirection4xx Client Error5xx Server ErrorCommon Patterns

1xx Informational

CommandDescription
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

CommandDescription
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

CommandDescription
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

CommandDescription
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

CommandDescription
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

CommandDescription
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

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