421 Misdirected Request

What is HTTP 421?

This status code indicates that the request was directed at a server that is not able to produce a response for it. This can happen when a server is not configured for the combination of scheme and authority in the request URI. It is most commonly associated with HTTP/2, where a single connection may be reused for multiple domains, but the server determines the connection is not appropriate for the requested host.

Defined in RFC 9110

Common Causes

• An HTTP/2 connection was reused for a domain the server does not handle
• TLS certificate mismatch where the connection's certificate does not cover the requested hostname
• Load balancer or reverse proxy routing the request to the wrong backend server

How to Fix

• Retry the request on a new connection to allow proper server routing
• Verify that the server's TLS certificate covers the requested domain name
• Check load balancer and reverse proxy configurations for correct host-based routing