HTTP 421 Misdirected Request
HTTP 421 Misdirected Request means the server that received the request is not able or willing to produce an authoritative response for the target URI. This is primarily an HTTP/2 issue, where connection reuse across multiple hostnames can result in requests being delivered to a server that does not handle that hostname.
Quick reference
| Code | 421 |
|---|---|
| Name | Misdirected Request |
| Category | 4xx Client Errors |
| Specification | RFC 9110 §15.5.20 |
| IANA status | Assigned |
| Cacheable | No |
| Client action | Retry the request over a new connection. The current connection cannot serve this host. |
| In-depth guide | HTTP 421 full guide → |
What HTTP 421 means
RFC 9110 defines 421 as indicating that the request was directed at a server that is not able to produce a response for that combination of scheme and authority. The server is essentially saying: this request was delivered to the wrong server, and I cannot authoritatively handle it.
The scenario most commonly: HTTP/2 allows multiple hostnames to share a single connection if they resolve to the same IP and the server's TLS certificate covers both hostnames (Subject Alternative Names). A client may reuse an existing HTTP/2 connection to send a request for a different hostname. If the server for that connection does not handle the second hostname — even though it is on the same IP and TLS certificate — it returns 421 to indicate the request must be sent on a separate connection.
Common causes
HTTP/2 connection reuse across virtual hosts
The client has an open HTTP/2 connection to server A (which handles api.example.com). It reuses that connection for a request to www.example.com because both resolve to the same IP and the TLS certificate covers both. If the server does not handle www.example.com on this connection, it returns 421.
Wildcard or multi-domain TLS certificate
A TLS certificate with a wildcard (*.example.com) or multiple SANs covers many hostnames. Clients may reuse a connection for any covered hostname, but not all hostnames may be served by the same virtual host configuration.
Reverse proxy misconfiguration
A reverse proxy that receives a request for a hostname it does not have a server block configured for may return 421 rather than a 404 or 500.
How to fix a 421
- Retry on a new connection. Most HTTP/2 clients that receive 421 automatically retry the request on a new connection. This is the expected behavior per RFC 9110.
- Configure the server to handle the hostname. If you control the server and it legitimately should handle the target hostname, add the appropriate virtual host or server block configuration.
- Disable HTTP/2 connection coalescing. Some clients have options to disable connection reuse across hostnames. This prevents 421 but reduces the performance benefit of HTTP/2.
FAQ
What does HTTP 421 Misdirected Request mean?
HTTP 421 means the server that received the request cannot produce a response for the target hostname. Retry the request — the client should open a new connection for the target hostname.
Why does 421 occur in HTTP/2 but not HTTP/1.1?
HTTP/1.1 connections are per-hostname. HTTP/2 allows connection reuse across hostnames that share an IP and TLS certificate. This reuse can route requests to a server not configured for that hostname, producing 421.
Will my browser automatically handle a 421?
Yes. Browsers that receive a 421 automatically retry the request over a new connection. End users typically do not see 421 errors — they are handled transparently by the browser.
Is 421 a server error or a client error?
It is a 4xx code, placed in the client error range. The "client" error is using connection reuse for a hostname the server cannot handle. The fix typically requires either a client retry or server reconfiguration.
Related resources
On this site: HTTP 421 Misdirected Request — full guide · HTTP 400 Bad Request · HTTP 503 Service Unavailable · All 4xx client errors
Standards: RFC 9110 §15.5.20 · IANA HTTP Status Code Registry · MDN Web Docs: 421