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4xx Client error

421 Misdirected Request

The request reached a server that can't answer for this domain.

What 421 means

With HTTP/2 connection reuse, a browser may send a request for one domain over a connection to a server that doesn't serve it.

Common causes

  • HTTP/2 connection coalescing across domains with a shared certificate.
  • TLS SNI and Host header mismatch.

How to fix it

If you're calling an API

  • Retry on a new connection (browsers do this automatically).

If you run the server

  • Check certificates and virtual-host configuration for domains sharing an IP.

Should you retry?

Yes, on a new connection.

Example response

HTTP
HTTP/1.1 421 Misdirected Request
Content-Type: application/problem+json

{
  "type": "about:blank",
  "title": "Misdirected Request",
  "status": 421,
  "detail": "The request reached a server that can't answer for this domain."
}

Defined in: RFC 9110 (HTTP Semantics). 421 is a client error: change the request before retrying.

Debugging an API call? Convert your request with the cURL converter, check the response with the JSON formatter, or see whether the API is down on its status page.

HTTP 421 FAQ

What does HTTP 421 mean?

421 Misdirected Request: The request reached a server that can't answer for this domain. With HTTP/2 connection reuse, a browser may send a request for one domain over a connection to a server that doesn't serve it.

Is 421 a client or server error?

It's a client error (4xx): something about the request needs to change before it can succeed.

How do I fix a 421 error?

Retry on a new connection (browsers do this automatically).

Should I retry after a 421?

Yes, on a new connection.

Other 4xx status codes

All HTTP status codes