494 Request Header Or Cookie Too Large

Unofficial · nginx

nginx found the request headers larger than its buffers allow. It can be caught with error_page; the client is sent 400.

What to do

nginx found the request headers too large and sends the client a 400. Clearing the site's cookies usually fixes it. On the server, raise large_client_header_buffers.

Class
4xx Client Error. The request has a fault, or cannot be met as sent.
Registered
No. nginx sends it, and it is not in the IANA registry, so other servers may mean something else by it.
References
nginx source

Every 4xx code

All HTTP status codes, in one table