421 Misdirected Request

The request reached a server that cannot answer for this domain.

Code: 421
Reason phrase: Misdirected Request
Class: 4xx Client error
Defined in: RFC 9110 section 15.5.20
Cacheable by default: No

What it means

Client error: the problem lies with the request. Repeating it unchanged will normally fail again.

Common causes. HTTP/2 connection reuse across domains that share an address but not a certificate, or a CDN routing problem.

What to do. Retry on a new connection. Site owners should check that the certificate and server names match.

How clients and crawlers treat it

Google Search. Like every 4xx except 429, it tells Google the content does not exist: an indexed URL is removed from the index, and a new one is not processed. Crawl frequency for the URL gradually drops. Source: Google Search Central, How HTTP status codes, and network and DNS errors affect Google Search.

Caching. Not cacheable by default (RFC 9110 section 15.1 does not list it). A cache stores it only when the response says so with Cache-Control or Expires.

Example response

HTTP/1.1 421 Misdirected Request
Content-Type: text/plain; charset=utf-8

Misdirected Request

How to send 421

nginx

location /example {
    return 421;
}

Apache (.htaccess)

RewriteEngine On
RewriteRule ^example$ - [R=421,L]

PHP

http_response_code(421);
echo 'Misdirected Request';
exit;

Node.js

res.writeHead(421, { 'Content-Type': 'text/plain' });
res.end('Misdirected Request');

Python (Flask)

# in a view function
return 'Misdirected Request', 421

Change the paths to suit. In nginx, add_header needs always to apply to error responses.

Related codes

All status codes · All 4xx codes

Names and numbers from the IANA HTTP Status Code Registry. Google Search behaviour as documented by Google Search Central.