431Request Header Fields Too Large
The request headers are too big for the server to accept, often because of cookies.
Browse all HTTP status codesWhen you see it
Accumulated cookies are the usual cause, since every one of them is sent with every request to that site. Long referrer URLs and oversized authentication tokens also contribute.
Clearing cookies for the site fixes it immediately from the visitor side. Some servers answer 400 in this situation instead, which makes the same problem much harder to identify.
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Status codes
69 of 69 codes. Click a row to copy it.
1xx Informational (4)
2xx Success (10)
3xx Redirection (8)
4xx Client errors (31)
5xx Server errors (16)