421 Misdirected Request

What does 421 Misdirected Request mean?

The request reached a server that is not configured to answer for that host name. It belongs to the 4xx Client Error class, which means the request contains bad syntax or cannot be fulfilled. Something about the request needs to change.

When do APIs return 421?

With HTTP/2 and HTTP/3, where a client may reuse one connection for several host names that share a certificate. If the server on that connection does not actually serve the second host, it answers 421. It also appears behind TLS-terminating proxies when the name in the TLS handshake and the Host header disagree.

How to fix a 421 Misdirected Request

Clients are allowed to retry the request on a fresh connection, and browsers do. If it persists, the fault is in the server or proxy configuration: check that the virtual host exists for that name, and that a proxy in front passes the same host name in SNI as in the Host header.

Reproduce a 421 response

The fastest way to understand a status code is to trigger one and read the full response. Open the API tester and send a request to https://httpbin.org/status/421 — you will see the 421 status along with every response header the server sent. Comparing those headers against a working request is often what reveals the cause.

When you are debugging a real endpoint, check the response headers as carefully as the body, and confirm you are using the right HTTP method for the operation.

Related 4xx status codes

See also

• 404 Not Found — The server cannot find the requested resource.

References

• RFC 9110, 421 Misdirected Request — The specification that defines this status code.
• MDN: 421 Misdirected Request — MDN's reference page for this status code.