What it means

A 431 response indicates the server is refusing to process the request because the headers are too large. This can happen when a single header is too long or when the total size of all headers exceeds the server's limit.

Common causes

• A cookie has grown too large.
• Too many custom headers were sent.
• An auth token in a header is excessively long.

How to fix it

• Reduce the size of cookies or other headers.
• Clear browser cookies for the site.
• If you are the developer, review what data is being sent in headers.