HTTP status codes are three-digit responses from web servers indicating the result of a request. They are grouped into five classes based on the first digit.
200
OK
301
Moved Permanently
304
Not Modified
404
Not Found
500
Server Error
503
Unavailable
Status Code Classes
1xx Informational | 2xx Success | 3xx Redirection | 4xx Client Error | 5xx Server Error
1xx Informational
Request received, continuing process
| Code | Name | Description |
|---|---|---|
| 100 | Continue | Server received request headers; client should proceed with body |
| 101 | Switching Protocols | Server is switching protocols as requested (e.g., to WebSocket) |
| 102 | Processing | Server has received request but not yet completed (WebDAV) |
| 103 | Early Hints | Used with Link header to preload resources while server prepares response |
2xx Success
Request successfully received, understood, and accepted
| Code | Name | Description |
|---|---|---|
| 200COMMON | OK | Standard success response. Body contains requested resource |
| 201COMMON | Created | Request succeeded and new resource was created (POST/PUT) |
| 202 | Accepted | Request accepted for processing but not yet completed |
| 203 | Non-Authoritative Info | Metadata from third-party copy, not origin server |
| 204COMMON | No Content | Success with no body to return. Common for DELETE requests |
| 205 | Reset Content | Success; client should reset the document view |
| 206 | Partial Content | Range request successful; body contains requested ranges |
| 207 | Multi-Status | Multiple status codes for multiple resources (WebDAV) |
| 208 | Already Reported | DAV binding already enumerated; prevents repeated listings |
| 226 | IM Used | Server fulfilled GET request with instance-manipulations |
3xx Redirection
Further action needed to complete the request
| Code | Name | Description |
|---|---|---|
| 300 | Multiple Choices | Multiple options for the resource; client may choose one |
| 301COMMON | Moved Permanently | Resource permanently moved. Use for permanent URL changes (SEO-friendly) |
| 302COMMON | Found | Temporary redirect. Method may change to GET (historically) |
| 303 | See Other | Redirect with GET to different URI (e.g., after POST) |
| 304COMMON | Not Modified | Cached version is still valid; no body sent |
| 305 | Use Proxy | Deprecated. Resource only available through proxy |
| 307 | Temporary Redirect | Temporary redirect; method and body unchanged |
| 308 | Permanent Redirect | Permanent redirect; method and body unchanged (like 301 but stricter) |
301 vs 302 vs 307 vs 308
301/308: Permanent (cached by browsers, SEO passes link equity). 302/307: Temporary (not cached, SEO keeps original).
301/302: May change POST to GET. 307/308: Method preserved (use for API redirects).
4xx Client Errors
Request contains bad syntax or cannot be fulfilled
| Code | Name | Description |
|---|---|---|
| 400COMMON | Bad Request | Malformed request syntax, invalid parameters |
| 401COMMON | Unauthorized | Authentication required. Include WWW-Authenticate header |
| 402 | Payment Required | Reserved for future use (digital payment systems) |
| 403COMMON | Forbidden | Server understood but refuses. Unlike 401, authenticating won't help |
| 404COMMON | Not Found | Resource does not exist at this URI |
| 405 | Method Not Allowed | HTTP method not supported for this resource |
| 406 | Not Acceptable | Resource cannot satisfy Accept headers |
| 407 | Proxy Auth Required | Like 401 but for proxy server authentication |
| 408 | Request Timeout | Server timed out waiting for the request |
| 409 | Conflict | Request conflicts with current state (e.g., edit conflict) |
| 410 | Gone | Resource permanently deleted. Unlike 404, it existed before |
| 411 | Length Required | Content-Length header required |
| 412 | Precondition Failed | Precondition header (If-Match, etc.) evaluated to false |
| 413 | Payload Too Large | Request body exceeds server limits |
| 414 | URI Too Long | Request URI exceeds server limits |
| 415 | Unsupported Media Type | Content-Type not supported by the endpoint |
| 416 | Range Not Satisfiable | Range header cannot be satisfied |
| 417 | Expectation Failed | Expect header cannot be met by server |
| 418 | I'm a Teapot | April Fools' joke (RFC 2324). Sometimes used to reject bots |
| 421 | Misdirected Request | Request directed at server unable to produce response |
| 422COMMON | Unprocessable Entity | Well-formed but semantically invalid (validation errors) |
| 423 | Locked | Resource is locked (WebDAV) |
| 424 | Failed Dependency | Request failed due to previous request failure (WebDAV) |
| 425 | Too Early | Server unwilling to process potentially replayed request |
| 426 | Upgrade Required | Client should upgrade to different protocol |
| 428 | Precondition Required | Server requires request to be conditional |
| 429COMMON | Too Many Requests | Rate limiting. Check Retry-After header |
| 431 | Headers Too Large | Request headers exceed server limits |
| 451 | Unavailable For Legal | Resource blocked for legal reasons (censorship, DMCA) |
401 vs 403
401 Unauthorized: Identity unknown. Provide credentials and retry.
403 Forbidden: Identity known but not permitted. Re-authenticating won't help.
5xx Server Errors
Server failed to fulfill a valid request
| Code | Name | Description |
|---|---|---|
| 500COMMON | Internal Server Error | Generic server error. Check server logs for details |
| 501 | Not Implemented | Server doesn't support functionality required |
| 502COMMON | Bad Gateway | Invalid response from upstream server (proxy/gateway) |
| 503COMMON | Service Unavailable | Server overloaded or down for maintenance |
| 504COMMON | Gateway Timeout | Upstream server didn't respond in time |
| 505 | HTTP Version Not Supported | Server doesn't support the HTTP version used |
| 506 | Variant Also Negotiates | Transparent content negotiation circular reference |
| 507 | Insufficient Storage | Server cannot store representation (WebDAV) |
| 508 | Loop Detected | Infinite loop detected while processing (WebDAV) |
| 510 | Not Extended | Further extensions required for the request |
| 511 | Network Auth Required | Client must authenticate to gain network access (captive portal) |
Unofficial but Common Codes
| Code | Name | Used By |
|---|---|---|
| 520 | Web Server Unknown Error | Cloudflare |
| 521 | Web Server Is Down | Cloudflare |
| 522 | Connection Timed Out | Cloudflare |
| 523 | Origin Is Unreachable | Cloudflare |
| 524 | A Timeout Occurred | Cloudflare |
| 525 | SSL Handshake Failed | Cloudflare |
| 526 | Invalid SSL Certificate | Cloudflare |
| 530 | Site Frozen | Pantheon |