The server is reluctant to process the request since its header fields are excessively huge. The request MAY be resubmitted subsequent to decreasing the size of the request header fields.
It tends to be utilized both when the arrangement of request header fields altogether is excessively huge, and when a solitary header field is to blame. In the last case, the reaction representation SHOULD determine which header field was excessively enormous.
HTTP/1.1 431 Request Header Fields Too Large
<title>Request Header Fields Too Large</title>
<h1>Request Header Fields Too Large</h1>
<p>The “Example” header was too large.</p>