Takeaways
- The server is unwilling to process the request because its header fields are too large.
- The request may be resubmitted after reducing the size of the request header fields.
- It can be used both when the set of request header fields in total is too large, and when a single header field is at fault.
- In the latter case, the response representation should specify which header field was too large.
Example
HTTP/1.1 431 Request Header Fields Too Large
Content-Type: text/html<html>
<head>
<title>Request Header Fields Too Large</title>
</head>
<body>
<h1>Request Header Fields Too Large</h1>
<p>The "Example" header was too large.</p>
</body>
</html>Responses with the 431 status code must not be stored by a cache.
Information
431 can be used when the total size of request headers is too large, or when a single header field is too large. To help those running into this error, indicate which of the two is the problem in the response body — ideally, also include which headers are too large. This lets users attempt to fix the problem, such as by clearing their cookies.