| 400 |
Bad Request |
Malformed syntax or invalid request. |
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| 401 |
Unauthorized |
Authentication required or failed. |
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| 402 |
Payment Required |
Reserved for future use. |
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| 403 |
Forbidden |
Server understood but refuses to authorize. |
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| 404 |
Not Found |
Resource not found. |
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| 405 |
Method Not Allowed |
Method not allowed for the target. |
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| 406 |
Not Acceptable |
No acceptable representation found. |
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| 407 |
Proxy Authentication Required |
Authenticate with proxy first. |
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| 408 |
Request Timeout |
Server timed out waiting for request. |
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| 409 |
Conflict |
Request conflicts with current state. |
 |
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| 410 |
Gone |
Resource permanently removed. |
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| 411 |
Length Required |
Content-Length header required. |
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| 412 |
Precondition Failed |
One or more preconditions failed. |
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| 413 |
Content Too Large |
Request payload is too large. |
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| 414 |
URI Too Long |
URI is too long to process. |
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| 415 |
Unsupported Media Type |
Unsupported payload media type. |
 |
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| 416 |
Range Not Satisfiable |
Requested range cannot be served. |
 |
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| 417 |
Expectation Failed |
Expect header requirements not met. |
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| 418 |
I’m a Teapot |
April Fools’/novelty; non-standard in practice. |
 |
|
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| 421 |
Misdirected Request |
Request routed to a server that can’t produce response. |
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| 422 |
Unprocessable Content (WebDAV) |
Well-formed but semantically erroneous. |
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| 423 |
Locked (WebDAV) |
Resource is locked. |
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| 424 |
Failed Dependency (WebDAV) |
Failed due to earlier request failure. |
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| 425 |
Too Early |
Risk of replay; try later. |
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| 426 |
Upgrade Required |
Must upgrade protocol (e.g., TLS/HTTP2). |
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| 428 |
Precondition Required |
Preconditions required on the request. |
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|
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| 429 |
Too Many Requests |
Rate limit exceeded. |
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| 431 |
Request Header Fields Too Large |
Header fields too large. |
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| 451 |
Unavailable For Legal Reasons |
Blocked for legal demands. |
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