← All HTTP status codes
451
Unavailable For Legal Reasons
Access is denied for legal reasons, such as censorship or court order.
The 4xx class
4xx, Client errors. The request itself is at fault: bad syntax (400), missing authentication (401), forbidden (403), missing resource (404) or rate limited (429).
Monitoring for this code
Client-error responses on your own health checks usually mean a deployment or configuration bug (wrong route, missing credentials, rate limiting). Monitor the exact expected code: a 404 where you expect 200 should page you, while an expected 401 on a protected endpoint can be asserted as healthy.
Other 4xx status codes
400 Bad Request401 Unauthorized402 Payment Required403 Forbidden404 Not Found405 Method Not Allowed406 Not Acceptable407 Proxy Authentication Required408 Request Timeout409 Conflict410 Gone411 Length Required412 Precondition Failed413 Content Too Large414 URI Too Long415 Unsupported Media Type416 Range Not Satisfiable417 Expectation Failed418 I'm a teapot421 Misdirected Request422 Unprocessable Content423 Locked424 Failed Dependency425 Too Early426 Upgrade Required428 Precondition Required429 Too Many Requests431 Request Header Fields Too Large
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