MDN wants to talk to developers like you: https://qsurvey.mozilla.com/s3/8d22564490d8

431 Request Header Fields Too Large

The HTTP 431 Request Header Fields Too Large response status code indicates that 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 when the total number of request header fields is too large, or when a single header field is at too large.

This error shouldn't happen on well-tested production systems, but can be found more often while testing a new system.

Status

431 Request Header Fields Too Large

Specifications

Specification Title
RFC 6585, section 5: 431 Request Header Fields Too Large Additional HTTP Status Codes

See also

Document Tags and Contributors

 Contributors to this page: teoli, fscholz
 Last updated by: teoli,