HTTP 421 — Misdirected Request
HTTP 421
Misdirected Request
The request arrived at a server that is not configured to answer for that hostname.
What 421 actually means
An HTTP/2 artefact. Browsers reuse one connection for several hostnames when the certificate covers them all, which is normally a performance win — but if the server behind that connection is not actually configured for the host being requested, it answers 421 to say "wrong door, open a new connection". Clients are expected to retry on a fresh connection, so a working setup will recover invisibly; a persistent 421 means the origin genuinely has no virtual host for that name.
Common causes
- HTTP/2 connection coalescing sending a request for host B down a connection opened for host A
- A wildcard or multi-domain certificate covering hostnames the origin does not serve
- A load balancer routing a request to a backend with no matching virtual host
- A missing or misconfigured `server_name` / `ServerName` entry
If you're just trying to view the page
- Reload the page — the browser usually retries on a new connection and succeeds
- Try a private window or another browser to rule out a coalesced connection being reused
- If it persists on one site only, it is a server configuration problem there
If it's your site
- Make sure every hostname on a shared certificate has a matching virtual host on every origin that certificate is served from
- Add an explicit default server block that returns 421 or 404 rather than silently serving the wrong site
- Watch for this after adding a SAN to a certificate but not the corresponding vhost
Reference
- Status code
- 421
- Reason phrase
- Misdirected Request
- Category
- 4xx — Client Error
- Defined in
- RFC 9110 §15.5.20
Common questions
- What does HTTP 421 mean?
- The request arrived at a server that is not configured to answer for that hostname. An HTTP/2 artefact. Browsers reuse one connection for several hostnames when the certificate covers them all, which is normally a performance win — but if the server behind that connection is not actually configured for the host being requested, it answers 421 to say "wrong door, open a new connection".
- How do I fix a 421 error?
- Reload the page — the browser usually retries on a new connection and succeeds
- Is 421 a client error or a server error?
- 421 is in the 4xx range, which means client error. The request itself was the problem, so retrying it unchanged will usually return the same code.
Related pages
- 404 Not Found The server is reachable and working, but there is nothing at the address you ask
- 403 Forbidden The server understood the request and is refusing to allow it, and logging in wi
- 401 Unauthorized You need to authenticate, and either you did not or your credentials were reject
- 429 Too Many Requests You have sent more requests than the service allows in a given period.
- 400 Bad Request The server could not understand the request because something about it is malfor
- 413 Content Too Large The request body is bigger than the server is willing to accept.
- 422 Unprocessable Content The request is well-formed and understood, but the data in it fails the rules.
- 405 Method Not Allowed The URL exists, but it does not accept the HTTP method you used.
- 409 Conflict The request cannot be completed because it clashes with the current state of the
- 415 Unsupported Media Type The server will not accept the format of the body you sent.
- 408 Request Timeout The server gave up waiting for the client to finish sending its request.
- 410 Gone The resource was deliberately removed and is not coming back, and there is no fo